The backtrace in comment 5 pretty much confirms that this is X crashing on logout.
** Package changed: kdebase-workspace (Ubuntu Lucid) => xserver-xorg- video-intel (Ubuntu Lucid) -- Non-admin user logout fails on Lucid https://bugs.launchpad.net/bugs/569879 You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-intel in ubuntu. _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp