Comment 3 for bug 1173262

I ran the unity-panel-service against the GLib already in the distribution and found that this critical is popping up:

(unity-panel-service.:17248): GLib-GObject-CRITICAL **: g_signal_handlers_disconnect_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(unity-panel-service.:17248): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `(null)'

(unity-panel-service.:17248): GLib-GObject-CRITICAL **: g_signal_handlers_disconnect_matched: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(unity-panel-service.:17248): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `(null)'

with a very similar backtrace to the one you found. This is pretty clearly a case of already-broken behaviour in Unity being pushed over the line by changes to memory layout.