If you are trying to disable KMS as a workaround (it worked for Maverick), in the Comment #4 of Bug #755791 , the user Bryce Harrington explained me that since in Natty the driver is not Radeon any more (it has been replaced by Gallium 3d drivers), that workaround will not work.
https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video- ati/+bug/755791/comments/4 Unfortunately the only options are: fixing the issue in this driver or using another driver (not a viable option since radeonhd and old radeon are deprecated). -- You received this bug notification because you are a member of Ubuntu-X, which is a direct subscriber. https://bugs.launchpad.net/bugs/556782 Title: [rs690m] Graphics corruption with ati x1200 _______________________________________________ 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