NNTPGrab

This isn't a bug in NNTPGrab, but a bug in the package gtk3-engines-oxygen which is part of KUbuntu 12.04.
To be exactly it is a stack overflow. Please report the following details to the KUbuntu bug tracker for the gtk3-engines-oxygen component:

kubuntu@kubuntu:~$ gdb nntpgrab_gui
GNU gdb (Ubuntu/Linaro 7.4-2012.02-0ubuntu2) 7.4-2012.02
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying" 
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
...
Reading symbols from /usr/bin/nntpgrab_gui...done.
(gdb) r
Starting program: /usr/bin/nntpgrab_gui 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffee6a6700 (LWP 6503)]
[New Thread 0x7fffedbdc700 (LWP 6504)]
[New Thread 0x7fffecda7700 (LWP 6507)]

(NNTPGrab:6500): Gtk-CRITICAL **: gtk_css_section_get_file: assertion `section != NULL' failed

(NNTPGrab:6500): Gtk-CRITICAL **: gtk_css_section_get_end_position: assertion `section != NULL' failed

(NNTPGrab:6500): Gtk-CRITICAL **: gtk_css_section_get_end_line: assertion `section != NULL' failed

(NNTPGrab:6500): Gtk-WARNING **: Theme parsing error: :1:0: Unknown value 'GTK_SHADOW_NONE' for enum type 'GtkShadowType'
[New Thread 0x7fffe7ac1700 (LWP 6508)]
[New Thread 0x7fffe72c0700 (LWP 6509)]
[Thread 0x7fffe7ac1700 (LWP 6508) exited]
[Thread 0x7fffe72c0700 (LWP 6509) exited]
[New Thread 0x7fffe72c0700 (LWP 6510)]
[Thread 0x7fffe72c0700 (LWP 6510) exited]
[New Thread 0x7fffe7ac1700 (LWP 6511)]
[New Thread 0x7fffd3385700 (LWP 6512)]
[Thread 0x7fffe7ac1700 (LWP 6511) exited]
[Thread 0x7fffd3385700 (LWP 6512) exited]

Program received signal SIGSEGV, Segmentation fault.
gtk_widget_compute_expand (widget=0x84f000, orientation=GTK_ORIENTATION_VERTICAL) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:11818
11818   /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c: No such file or directory.
(gdb) bt
#0  gtk_widget_compute_expand (widget=0x84f000, orientation=GTK_ORIENTATION_VERTICAL) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:11818
#1  0x00007ffff6fc7217 in count_expand_children (box=, visible_children=0x7fffff7ff0c0, expand_children=0x7fffff7ff0c4)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:415
#2  0x00007ffff6fc7982 in gtk_box_size_allocate (widget=, allocation=0x7fffff7ff660)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:447
#3  0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4  0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5  0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6  0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#7  0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#8  0x00007ffff700af53 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1790
#9  0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#10 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#11 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#12 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#13 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=19503, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#14 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#15 0x00007fffe7d1df3a in Oxygen::Animations::sizeAllocationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#16 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#17 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#18 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#19 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f240, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#20 0x00007ffff705c504 in gtk_frame_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkframe.c:786
#21 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#22 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#23 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#24 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#25 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f000, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#26 0x00007ffff6fc7cb0 in gtk_box_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:658
#27 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#28 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#29 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#30 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#31 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#32 0x00007ffff700af53 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1790
#33 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#34 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#35 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#36 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#37 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=19489, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#38 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#39 0x00007fffe7d1df3a in Oxygen::Animations::sizeAllocationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#40 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#41 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#42 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#43 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f240, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#44 0x00007ffff705c504 in gtk_frame_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkframe.c:786
#45 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#46 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#47 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#48 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#49 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f000, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#50 0x00007ffff6fc7cb0 in gtk_box_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:658
#51 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#52 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#53 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#54 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#55 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#56 0x00007ffff700af53 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1790
#57 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#58 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#59 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#60 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#61 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=19475, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409

<>

#33327 0x00007ffff700aeb6 in gtk_container_resize_children (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1825
#33328 0x00007ffff700af70 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1798
#33329 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33330 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33331 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33332 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#33333 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=71, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#33334 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33335 0x00007fffe7d1df3a in Oxygen::Animations::sizeAllocationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33336 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33337 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33338 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33339 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f240, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33340 0x00007ffff705c504 in gtk_frame_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkframe.c:786
#33341 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33342 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33343 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33344 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33345 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f000, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33346 0x00007ffff6fc7cb0 in gtk_box_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:658
#33347 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33348 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33349 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33350 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33351 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33352 0x00007ffff700aeb6 in gtk_container_resize_children (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1825
#33353 0x00007ffff700af70 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1798
#33354 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33355 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33356 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33357 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#33358 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=57, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#33359 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33360 0x00007fffe7d1df3a in Oxygen::Animations::sizeAllocationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33361 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33362 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33363 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33364 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f240, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33365 0x00007ffff705c504 in gtk_frame_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkframe.c:786
#33366 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33367 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33368 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33369 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33370 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f000, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33371 0x00007ffff6fc7cb0 in gtk_box_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:658
#33372 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33373 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33374 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33375 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33376 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33377 0x00007ffff700aeb6 in gtk_container_resize_children (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1825
#33378 0x00007ffff700af70 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1798
#33379 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33380 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33381 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33382 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#33383 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=43, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#33384 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33385 0x00007fffe7d1df3a in Oxygen::Animations::sizeAllocationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33386 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33387 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33388 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33389 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f240, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33390 0x00007ffff705c504 in gtk_frame_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkframe.c:786
#33391 0x00007ffff51ddc1b in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33392 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33393 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33394 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33395 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x84f000, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33396 0x00007ffff6fc7cb0 in gtk_box_size_allocate (widget=, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:658
#33397 0x00007ffff51ddca2 in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33398 0x00007ffff51ef179 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33399 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33400 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33401 0x00007ffff71cc1a9 in gtk_widget_size_allocate (widget=0x832860, allocation=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4992
#33402 0x00007ffff700aeb6 in gtk_container_resize_children (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1825
#33403 0x00007ffff700af70 in gtk_container_real_check_resize (container=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:1798
#33404 0x00007ffff51ddeca in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33405 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33406 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33407 0x00007ffff710b7d0 in queue_resize_on_widget (widget=0x84f240, check_siblings=, flags=0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtksizegroup.c:290
#33408 0x00007ffff71c6b98 in gtk_widget_set_usize_internal (widget=0x84f240, width=53, height=29, flags=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9409
#33409 0x00007fffe7d242f2 in Oxygen::GroupBoxLabelEngine::adjustSize(_GtkWidget*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33410 0x00007fffe7d1e31a in Oxygen::Animations::realizationHook(_GSignalInvocationHint*, unsigned int, _GValue const*, void*) ()
   from /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/theming-engines/liboxygen-gtk.so
#33411 0x00007ffff51ee9c5 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33412 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33413 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33414 0x00007ffff71c7c40 in gtk_widget_realize (widget=0x84f240) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4507
#33415 0x00007ffff71c81c8 in gtk_widget_map (widget=0x84f240) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4277
#33416 0x00007ffff700b22f in gtk_container_map (widget=0x84f000) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:3228
#33417 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33418 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33419 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33420 0x00007ffff71c80ba in gtk_widget_map (widget=0x84f000) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4279
#33421 0x00007ffff6fc7054 in gtk_box_forall (container=, include_internals=, 
    callback=0x7ffff7007fe0 , callback_data=0x0) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:1856
#33422 0x00007ffff700b22f in gtk_container_map (widget=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:3228
#33423 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33424 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33425 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33426 0x00007ffff71c80ba in gtk_widget_map (widget=0x832860) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4279
#33427 0x00007ffff6fc7054 in gtk_box_forall (container=, include_internals=, 
    callback=0x7ffff7007fe0 , callback_data=0x0) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:1856
#33428 0x00007ffff700b22f in gtk_container_map (widget=0x7ff620) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:3228
#33429 0x00007ffff51dde3c in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33430 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33431 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33432 0x00007ffff71c80ba in gtk_widget_map (widget=0x7ff620) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4279
#33433 0x00007ffff6fc7054 in gtk_box_forall (container=, include_internals=, 
    callback=0x7ffff7007fe0 , callback_data=0x0) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkbox.c:1856
#33434 0x00007ffff700b22f in gtk_container_map (widget=0x7ff550) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkcontainer.c:3228
#33435 0x00007ffff51ddeca in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33436 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33437 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33438 0x00007ffff71c80ba in gtk_widget_map (widget=0x7ff550) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:4279
#33439 0x00007ffff71c82fc in gtk_widget_set_child_visible (widget=0x7ff550, is_visible=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:9070
#33440 0x00007ffff70c18bb in gtk_notebook_real_switch_page (notebook=0x793450, child=, page_num=)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtknotebook.c:6574
#33441 0x00007ffff51ddca2 in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33442 0x00007ffff51ef339 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33443 0x00007ffff51f7099 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33444 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33445 0x000000000040c243 in on_cat_selection_changed (selection=, data=) at config.c:50
#33446 0x00007ffff51ddeca in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33447 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33448 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33449 0x00007ffff71a1e84 in gtk_tree_view_real_set_cursor (tree_view=0x7f4020, path=0x9119c0, flags=3)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtktreeview.c:13287
#33450 0x00007ffff71a5b06 in gtk_tree_view_button_press (widget=0x7f4020, event=0xe3f0a0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtktreeview.c:3133
#33451 0x00007ffff7092331 in _gtk_marshal_BOOLEAN__BOXEDv (closure=0x646ae0, return_value=0x7fffffffceb0, instance=0x7f4020, 
    args=, marshal_data=, n_params=, param_types=0x646b10)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkmarshalers.c:130
#33452 0x00007ffff51ddeca in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33453 0x00007ffff51f6741 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33454 0x00007ffff51f7242 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#33455 0x00007ffff71bd779 in gtk_widget_event_internal (widget=0x7f4020, event=0xe3f0a0) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkwidget.c:6380
#33456 0x00007ffff70901db in propagate_event_up (topmost=, event=, widget=0x7f4020)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkmain.c:2404
#33457 propagate_event (widget=, event=0xe3f0a0, captured=, topmost=0x0)
    at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkmain.c:2504
#33458 0x00007ffff7091ef1 in gtk_main_do_event (event=0xe3f0a0) at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkmain.c:1717
#33459 0x00007ffff6ce1d12 in gdk_event_source_dispatch (source=, callback=, user_data=)
    at /build/buildd/gtk+3.0-3.4.1/./gdk/x11/gdkeventsource.c:358
#33460 0x00007ffff4f20c9a in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33461 0x00007ffff4f21060 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33462 0x00007ffff4f2145a in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33463 0x00007ffff709125d in gtk_main () at /build/buildd/gtk+3.0-3.4.1/./gtk/gtkmain.c:1165
#33464 0x000000000040bd9a in main (argc=1, argv=0x7fffffffe208) at main.c:576
(gdb) 

With this information the package maintainers of the gtk3-engines-oxygen component should be able to resolve this issue

A quick workaround for you would be to select a different theme engine or install the nntpgrab-gui-qt package (which provides a more KDE friendly user interface for NNTPGrab)