Thank you for your bug. Could you attach your /var/log/messages,
/var/log/syslog and /var/log/Xorg.0.log? Does it happen if you use the
ati driver?
** Changed in: gdm (Ubuntu)
Importance: Undecided => Medium
Status: Unconfirmed => Needs Info
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logout leads to crash (feisty)
https://launchpad.net/bugs/94370