Fast User Switch leads to black screen

Hi list,

I'm using Gnome 2.24.1 (in Ubuntu 8.10) on a Thinkpad X60s (with Intel
graphics) and the fast-user-switch-applet doesn't work at all.
Switching from user A to user B works normally but switching back to
user A always leads to black screen with just the mouse curser on it.
I have to restart gdm then to be able to log in to gnome again.
I have another computer running the same Ubuntu version with the same
Gnome version where the fast user switching works like a charm.

Could anyone give me a hint or even some assistance on how to find the
source of the problem (e.g. are there any log files I could examine?).

Cheers
--

-- 
Moritz Reiter