switching users kills first user

[Ross Boylan <RossBoylan@stanfordalumni.org>]

For at least the last month, sometimes when I switch user (as in "switch
user" from the KDE menu) to another user's session, the session for the
first user is killed.

This has happened with 2 or 3 user sessions.  It has happened when
switching from the first session (vt7) or the 2nd (vt8).  The session
killed usually is using a lot of memory, but there is still quite a bit
of virtual memory left.

Is anyone else seeing this?  Any suggestions for what to do?  I don't
even know what package I would file a bug against--if anyone knows, I'd
love to hear it.

Thanks.
Ross

Currently, 
kdebase 4:3.5.7-4
linux-image-2.6.18-5-686             2.6.18.dfsg.1-13etch3
xorg                                 1:7.2-5 
nvidia-glx                           1.0.8776-4
nvidia-kernel-2.6.18-5-686           1.0.8776+6etch1
The free nvidia driver does not work with my card, a GeForce 6600 LE.
There have been some point releases of the kernel since the nvidia
stuff; I'm not sure if it needs to be updated to match the kernel
exactly or not.

I've founding nothing useful in the logs, just 
Sep 27 19:34:02 corn kdm[7491]: X server for display :0 terminated
unexpectedly