I don't know what distro you upgrade, but until sarge, you could use "dpkg-reconfigure xserver-xfree86" to solve this kind of problems.
This person is using Testing, and the error happened after an upgrade. We tried dpkg-reconfigure xserver-xfree86, mostly to change video drivers, but it is not working. -- Leonid Grinberg lgrinberg@gmail.com http://www.lgrinberg.org