gnome-panel hangs

[Nils Kanning <nils@kanning.de>]

hi,
i'm using gnome 2.8 with debian sarge and kernel 2.6.8.
while using nautilus or opening dialogs e. g. wlan-applet preferences 
these applications randomly freeze. then after selecting "force quit" 
text and icons on my gnome-panel are not rendered anylonger.
afterwards my ~/.xsession-error shows the following:
(gnome-session:3507) Gdk-CRITICAL **: file gdkdraw.c: line 651 
(gdk_draw_drawable): assertion 'src != NULL failed

any ideas?

nils