Comment 4 for bug 226993

It looks like there is still an old xorg.conf in use, used in a previous version. But the one for xorg 7.3 doesn't need that much information, it can even screw things up.
Please try if everything is solved after you've executed the command 'sudo dpkg-reconfigure xserver-xorg'. If you don't know what you should insert, press enter and the default or already existing settings will be kept. Make sure you restart the X server afterwards.