According to https://bugzilla.kernel.org/show_bug.cgi?id=30052#c17 this seems to be fixed in recent kernel releases. I think that the patches fixing it should be backported!
> I can't reproduce this bug on 2.6.39-git19 and 3.0-rc3. > Seems bug fixed. > Thanks! -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-ati in Ubuntu. https://bugs.launchpad.net/bugs/727620 Title: [Radeon HD 5650 and 5470] Kernel BUG during recovery boot and in normal boot (Hybrid graphics) To manage notifications about this bug go to: https://bugs.launchpad.net/linux/+bug/727620/+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
