I think it is the same bug but symptoms are slighty not the same. But I don't know how to recognize this bug in the logs. I put in attachment the kern.log when the boot failed.
** Attachment added: "Fail.txt" https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/727620/+attachment/2186877/+files/Fail.txt -- 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