Looks like a tiling bug - in particular you have a machine susceptible to the L-shape tiling bug.
** Summary changed: - Corrupted painting of window surfaces + [gm45] Corrupted painting of window surfaces (L-shape tiling corruption?) -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/1222871 Title: [gm45] Corrupted painting of window surfaces (L-shape tiling corruption?) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1222871/+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