It sounds suspiciously like this is a bug in the nouveau driver, since it only occurs when using the nouveau driver and not the nVidia driver, and has not been reported against the intel or AMD drivers.
** Changed in: unity (Ubuntu) Status: New => Triaged ** Also affects: xserver-xorg-video-nouveau (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-nouveau in Ubuntu. https://bugs.launchpad.net/bugs/1232940 Title: appearing color bar instead of unity and panel To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1232940/+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