Comment 36 for bug 575160

May be it's something like this:

<http://mail.gnome.org/archives/gtk-app-devel-list/2006-April/msg00255.html> ?

Are you using threads? If so... You may have to protect the gtk calls
you make inside the timeout function using gtk_threads_enter/leave()
pair... I haven't bothered to look into the long backtrace... So it is
just an assumption...

timeout functions are not called within the GTK lock.

timeout_fn(...)
{
   other_call();
   ....
   gtk_threads_enter();
   my_gtk_call();
   gtk_threads_leave();
}

Regards,
Santhosh.