Comment 7 for bug 568779

It's impossible to reach the recovery mode of such installation, so I have installed a clean installation on another partition, and chroot into the buggy one, and did
dpkg-reconfigure xserver-xorg
=> Rebooted and no luck :(

Amazing... The same 2.6.32-21-generic kernel, but one with clean installation, one with upgraded installation, the result is different. So is the problem with the video drivers, not with the kernel?