Is this "Gdk-WARNING **: XID collision, trouble ahead" important?

[Chris G]

I get the following messages in my .xsession-errors every time I start X:-

    (xfce4-terminal:5622): Gdk-WARNING **: XID collision, trouble ahead

    (polkit-gnome-authentication-agent-1:5856): GLib-GObject-WARNING **: cannot register existing type `_PolkitError'

    (polkit-gnome-authentication-agent-1:5856): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed

Nothing much actually seems to be wrong so should I worry about these?

-- 
Chris Green