Yes. I believe I enabled accessibility support just before this started happening. I've since disabled accessibility from the Universal Access app, but crash is still happening.

Here is a better backtrace (sorry, last one is missing gobject debug symbols):

Program received signal SIGSEGV, Segmentation fault.
g_type_check_instance_cast (type_instance=0x8164ac0, iface_type=134665448) at /build/buildd/glib2.0-2.29.16/./gobject/gtype.c:3985
3985	/build/buildd/glib2.0-2.29.16/./gobject/gtype.c: No such file or directory.
	in /build/buildd/glib2.0-2.29.16/./gobject/gtype.c
(gdb) bt
#0  g_type_check_instance_cast (type_instance=0x8164ac0, iface_type=134665448) at /build/buildd/glib2.0-2.29.16/./gobject/gtype.c:3985
#1  0x0048b88a in ?? () from /usr/lib/libgtk-3.so.0
#2  0x0081e9fa in g_cclosure_marshal_VOID__PARAM (closure=0x8101be8, return_value=0x0, n_param_values=2, param_values=0x81f8ef0, invocation_hint=0xbfffea70, 
    marshal_data=0x0) at /build/buildd/glib2.0-2.29.16/./gobject/gmarshal.c:539
#3  0x0081ca5c in g_closure_invoke (closure=0x8101be8, return_value=0x0, n_param_values=2, param_values=0x81f8ef0, invocation_hint=0xbfffea70)
    at /build/buildd/glib2.0-2.29.16/./gobject/gclosure.c:773
#4  0x00830ec0 in signal_emit_unlocked_R (node=0x805df28, detail=96, instance=0x815d158, emission_return=0x0, instance_and_params=0x81f8ef0)
    at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3271
#5  0x00839b8f in g_signal_emit_valist (instance=0x815d158, signal_id=1, detail=96, var_args=0xbfffec20 "\300\244\024\b\002")
    at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3002
#6  0x00839d03 in g_signal_emit (instance=0x815d158, signal_id=1, detail=96) at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3059
#7  0x0081fe1f in g_object_dispatch_properties_changed (object=0x815d158, n_pspecs=1, pspecs=0xbfffec90) at /build/buildd/glib2.0-2.29.16/./gobject/gobject.c:925
#8  0x0081f17f in g_object_notify_dispatcher (object=0x815d158, n_pspecs=1, pspecs=0xbfffec90) at /build/buildd/glib2.0-2.29.16/./gobject/gobject.c:331
#9  0x00822392 in g_object_notify_queue_thaw (nqueue=<optimized out>, object=0x815d158) at /build/buildd/glib2.0-2.29.16/./gobject/gobjectnotifyqueue.c:132
#10 g_object_notify_by_spec_internal (pspec=<optimized out>, object=0x815d158) at /build/buildd/glib2.0-2.29.16/./gobject/gobject.c:983
#11 g_object_notify (object=0x815d158, property_name=0x55b566 "visible") at /build/buildd/glib2.0-2.29.16/./gobject/gobject.c:1024
#12 0x00421f0d in gtk_widget_show () from /usr/lib/libgtk-3.so.0
#13 0x0125e291 in ?? () from /usr/lib/libdbusmenu-gtk3.so.4
#14 0x0081ec6a in g_cclosure_marshal_VOID__OBJECT (closure=0x817db08, return_value=0x0, n_param_values=2, param_values=0x81f8ec8, invocation_hint=0xbfffee90, 
    marshal_data=0x0) at /build/buildd/glib2.0-2.29.16/./gobject/gmarshal.c:644
#15 0x0081ca5c in g_closure_invoke (closure=0x817db08, return_value=0x0, n_param_values=2, param_values=0x81f8ec8, invocation_hint=0xbfffee90)
    at /build/buildd/glib2.0-2.29.16/./gobject/gclosure.c:773
#16 0x00830ec0 in signal_emit_unlocked_R (node=0x8169758, detail=0, instance=0x80cb9a0, emission_return=0x0, instance_and_params=0x81f8ec8)
    at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3271
#17 0x00839b8f in g_signal_emit_valist (instance=0x80cb9a0, signal_id=200, detail=0, var_args=0xbffff040 "\001")
    at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3002
#18 0x00839d03 in g_signal_emit (instance=0x80cb9a0, signal_id=200, detail=0) at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3059
#19 0x0127804e in ?? () from /usr/lib/libdbusmenu-glib.so.4
#20 0x00706172 in g_simple_async_result_complete (simple=0x8139c50) at /build/buildd/glib2.0-2.29.16/./gio/gsimpleasyncresult.c:749
#21 0x00764a8b in reply_cb (connection=0x8122010, res=0x81679a0, user_data=0x8139c50) at /build/buildd/glib2.0-2.29.16/./gio/gdbusproxy.c:2482
#22 0x00706172 in g_simple_async_result_complete (simple=0x81679a0) at /build/buildd/glib2.0-2.29.16/./gio/gsimpleasyncresult.c:749
#23 0x00759a48 in g_dbus_connection_call_done (source=0x8122010, result=0x816a760, user_data=0xb6c1b020) at /build/buildd/glib2.0-2.29.16/./gio/gdbusconnection.c:5040
#24 0x00706172 in g_simple_async_result_complete (simple=0x816a760) at /build/buildd/glib2.0-2.29.16/./gio/gsimpleasyncresult.c:749
#25 0x007062ac in complete_in_idle_cb (data=0x816a760) at /build/buildd/glib2.0-2.29.16/./gio/gsimpleasyncresult.c:761
#26 0x008a66e0 in g_idle_dispatch (source=0x811f2d8, callback=0x706280 <complete_in_idle_cb>, user_data=0x816a760)
    at /build/buildd/glib2.0-2.29.16/./glib/gmain.c:4780
#27 0x008aa81f in g_main_dispatch (context=0x8087ae0) at /build/buildd/glib2.0-2.29.16/./glib/gmain.c:2439
#28 g_main_context_dispatch (context=0x8087ae0) at /build/buildd/glib2.0-2.29.16/./glib/gmain.c:3008
#29 0x008aaf50 in g_main_context_iterate (context=0x8087ae0, block=9148688, dispatch=1, self=<optimized out>) at /build/buildd/glib2.0-2.29.16/./glib/gmain.c:3086
#30 0x008ab55b in g_main_loop_run (loop=0xb6c06d20) at /build/buildd/glib2.0-2.29.16/./glib/gmain.c:3294
#31 0x002ab805 in gtk_main () from /usr/lib/libgtk-3.so.0
#32 0x0804af46 in main ()