What's really interesting me is that some of those failed assertions you posted showed up in 2006 for a completely different package: https://bugs.launchpad.net/ubuntu/+source/grip/+bug/41601 It makes me wonder if the GTK_IS_WIDGET hiccup is not Firefox's fault. I failed that assertion a few times in Firefox also: ============================================================================== GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin name. GCJ PLUGIN: thread 0x805e090: NP_GetValue return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin description. GCJ PLUGIN: thread 0x805e090: NP_GetValue return ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin name. GCJ PLUGIN: thread 0x805e090: NP_GetValue return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin description. GCJ PLUGIN: thread 0x805e090: NP_GetValue return (firefox:11111): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:11111): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:11111): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:11111): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed call failed Error: No running window found ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) GCJ PLUGIN: thread 0x805e0f0: NP_GetMIMEDescription GCJ PLUGIN: thread 0x805e0f0: NP_GetMIMEDescription return GCJ PLUGIN: thread 0x805e0f0: NP_GetValue GCJ PLUGIN: thread 0x805e0f0: NP_GetValue: returning plugin name. GCJ PLUGIN: thread 0x805e0f0: NP_GetValue return GCJ PLUGIN: thread 0x805e0f0: NP_GetValue GCJ PLUGIN: thread 0x805e0f0: NP_GetValue: returning plugin description. GCJ PLUGIN: thread 0x805e0f0: NP_GetValue return ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) GCJ PLUGIN: thread 0x805e0f0: NP_GetMIMEDescription GCJ PLUGIN: thread 0x805e0f0: NP_GetMIMEDescription return GCJ PLUGIN: thread 0x805e0f0: NP_GetValue GCJ PLUGIN: thread 0x805e0f0: NP_GetValue: returning plugin name. GCJ PLUGIN: thread 0x805e0f0: NP_GetValue return GCJ PLUGIN: thread 0x805e0f0: NP_GetValue GCJ PLUGIN: thread 0x805e0f0: NP_GetValue: returning plugin description. GCJ PLUGIN: thread 0x805e0f0: NP_GetValue return (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (firefox:2964): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed Error: No running window found ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) ** Message: GetValue variable 1 (1) ** Message: GetValue variable 2 (2) GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription GCJ PLUGIN: thread 0x805e090: NP_GetMIMEDescription return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin name. GCJ PLUGIN: thread 0x805e090: NP_GetValue return GCJ PLUGIN: thread 0x805e090: NP_GetValue GCJ PLUGIN: thread 0x805e090: NP_GetValue: returning plugin description. GCJ PLUGIN: thread 0x805e090: NP_GetValue return Segmentation fault ============================================================================== Stupidly, I have absolutely no idea what I was doing at the time, and can't reproduce it. I also can't reproduce your result* on 32-bit Xubuntu Hardy. Could be cause it's the 32bit version bt I will try to remember to check under Gnome and such later instead of XFCE. ** The upload sites you guys link to do not generate anything out of place for me.. Naturally if I can't reproduce it under 32 bit then it strongly suggests that your supposition about it being related to that other bug is correct? If I can reproduce it I will try to attach some of this: https://wiki.ubuntu.com/DebuggingProgramCrash -- maybe that will contain something useful, maybe not So anyway all in all is I think that there is some other problem causing the GTK_IS_WIDGET assertions to fail - it's curious that I have generated those warnings but don't know how to replicate them.. Maybe it will turn into a second bug. I am a lay person and know nothing but yeah, I am bold enough to suggest that if some other program had been also failing this assertion then perhaps something might be unhinged in gtk or elsewhere?? Maybe a couple of things? I hope I don't get in the way...