Comment 3 for bug 55224

tas50, Étienne, thanks for the bug report!

Unfortunately we really need more information before we can do anything.

Please follow https://help.ubuntu.com/community/DebuggingXAutoconfiguration, and attach the asked files into this bug report.

I'm also marking this bug for the right package (xserver-xorg-video-ati), since it is quite likely a driver problem.