X being unstable in F9?

Dear lazy web, I just hit a strange bug again that I know not at all how to handle. My screen just went all "broken" - some sort of black/purple/I-don't-remember-the-other-colours pattern was displayed there - meaning the X was dead. I knew that something's wrong because it hasn't happened for the first time and in the past I was more patient and tried to do something with that state. If I wait, X restarts but goes wrong again and this repeats several times until it stays in the broken state. The only thing I can do is to turn the computer off by hitting the power button which inhibits correct turn off of the computer - meaning the kernel is still accepting messages and working but the broken X block every keyboard input. If I recall correctly, I can still see and move the mouse pointer.

This happens really scarce, so scarce I don't remember what I was doing when it happened last time, but this time it happened when I tried to switch tabs in firefox and I have a feeling it happened in a similar situation before, but I don't remember. So in case this happens again, next time I can check with this post if the situation is same...

And until then, can someone directs me what to do? I tried looking in XOrg.log and /var/log/messages but there does not seem to be anything indicating the problem. I don't know what's causing it, where the bug is, how to triage it. Does anyone have similar experience or even better already know about a bug that's causing this? Or know where else can I look to for more info? I'd appreciate any input.

I have an intel video card and appart from having metacity 2.23.21 pulled from rawhide with compositing turned on I have pretty much ordinary, up-to-date F9 environment...

UPDATE: As per mcepl's suggestion, I've filled a bug against xserver. Hope it helps. If you suffer similar issue, leave your comments and logs there.
https://bugzilla.redhat.com/show_bug.cgi?id=464878