Comment 5 for bug 421842

Well, we probably should start by ruling out the not-smooth upgrade. Would you mind booting the alpha-4 livecd again, updating it to latest karmic, and restarting X (log out / log in should do it)? Or alternatively, alpha-5 will be out in a couple days if you'd like to wait and test that.

If you find you can't reproduce it like that, then the next question would be to see if some packages got messed up. You could do this by purging and reinstalling mesa, xorg-server, and -ati. See https://wiki.ubuntu.com/X/Troubleshooting/FglrxInteferesWithRadeonDriver for an example of the commands to do this (even though you didn't have -fglrx installed, the procedure for resetting -ati should be similar.)