It's been 1 month and no answer so based on the fact that removing the cdemu daemon remedied the problem, I'm going to presume it was a vhba issue and most likely already fixed upstream (current version works fine on kernel 3.0.0 or prior). Marking as Invalid bug for xorg-server.
** Changed in: xorg-server (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg-server in Ubuntu. https://bugs.launchpad.net/bugs/768893 Title: System crashes when cdemu is present To manage notifications about this bug go to: https://bugs.launchpad.net/cdemu/+bug/768893/+subscriptions _______________________________________________ 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