This problem it's due by the current feisty xorg 7.2 migration, wait until migration finished : https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/84731
This problem it's due by the current feisty xorg 7.2 migration, wait until migration finished : https:/ /bugs.launchpad .net/ubuntu/ +source/ xorg/+bug/ 84731