I am also attaching .xsession-errors file. Note that earlier in the day, compiz had crashed and reopened automatically. But that doesn't always happen, AFAIK.
** Attachment added: "xsession-errors" https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/980519/+attachment/3660441/+files/xsession-errors -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to nvidia-graphics-drivers in Ubuntu. https://bugs.launchpad.net/bugs/980519 Title: Random log off in Ubuntu 12.04 LTS To manage notifications about this bug go to: https://bugs.launchpad.net/unity/+bug/980519/+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