Comment 21 for bug 447892

Michael, there is no such thing as "the bug" that causes X to freeze, so you may or may not have the same bug as kalessin. An analogy would be bugs in a flight computer that cause a plane to fall down. As you probably understand such a bug could be in any number of places in the flight critical code. Bugs like this also typically only manifest itself on certain systems because of some particularities of the motherboard etc, so there probably was no way to predict that your system would freeze other than to test a LiveCD.

You may help to resolve this by filing a new bug report and providing the same information that kalassin has provided (see https://wiki.ubuntu.com/X/Troubleshooting/Freeze). Or you may wait and see if the fix for this bug fixes your problem as well.