Comment 109 for bug 127101

Oh, I forgot to mention. Yes, my filesystem is indeed XFS. I don't want to start a philosophical discussion about the right file system, but I consider XFS a good journaling file system and the symptoms are very clear to me, just calling sync before doing something just saved me another restore-session when the bug occured again. Maybe XFS's deferred allocation adds to the kernel's write cache, but for enthusiasts I think XFS should not be uncommon as it usually performs better on a stable system and does not use the same old data structures that ext2 uses for some 15 years.

Anyway -- here is a little update (after which I'm not so sure if my bug really is the same bug as reported by others here):
Running metacity (no compositing) and VLC as video player, still using XAA. After playing a video with the Xvideo output module, stopping the video and switching to a VT, I first experienced an immediate return to a frozen X while Caps Lock and Num Lock still works (the LEDs go on) but no Ctrl-Alt-Backsp. After some time, X restarted itself bringing me back a functional desktop. On a second attempt (after a warm restart of the computer) of the same procedure, I could switch to the VT the first time, after returning to X and repeating the video playback and switching to a VT, I got the gray blocks and a total system freeze.

The fact that X was able to recover itself in the first attempt makes me not so sure anymore if my bug really is related to the one being described here.