Comment 3 for bug 609938

This happens every time Ubuntu updates their kernel and/or Xorg version and leaves the old fglrx driver in place that was never designed to work with those new X.org and kernel versions.

Maybe one way to save users this kind of trouble in the future would be to add versioned dependencies to fglrx to make it conflict with kernel or X.org versions newer than what was in the last stable Ubuntu release. This way, if a user explicitly or implicitly updates their X.org or kernel to a new major version, they'd be forced to uninstall fglrx first.