X Error of failed request: BadAtom (invalid Atom parameter)

[froinds]

Hi
When I launch a gnome-session over ssh forwarded to my G5, I get this 
error on the G5 Apple's X11 xterm

X Error of failed request: BadAtom (invalid Atom parameter)
        Major opcode of failed request: 18 (X_ChangeProperty)
        Atom id in failed request: 0xf7
        Serial number of failed request: 13

what does that mean and how can I fix it?
My debian runs on a Beige G3 266 without a monitor. I connect to it via 
ssh from a G5.
Thanks
Froinds