Intel and Xorg freeze - what may be the problem?

[Łukasz Maśko]

Today I got my Xorg display (under KDE) frozen. Keyboard and mouse were 
responding, but nothing was changing on the display (but mouse pointer, 
which moved). What was interesting, was a message in the console:

(EE) intel(0): Failed to submit batch buffer, expect rendering corruption or 
even a frozen display: Input/output error.
intel_bufmgr_gem.c:1060: Error setting domain 11869: Input/output error

In the same time, in syslog I got this:

Apr 20 08:37:10 laptok kernel: : [drm:i915_hangcheck_elapsed] *ERROR* 
Hangcheck timer elapsed... GPU hung
Apr 20 08:37:10 laptok kernel: : render error detected, EIR: 0x00000000
Apr 20 08:37:10 laptok kernel: : [drm:i915_do_wait_request] *ERROR* 
i915_do_wait_request returns -5 (awaiting 2935568 at 2935567)

What may be the reason my laptop behaved like this? Usually my machine is 
rock steady. I'm using intel driver 2.11.0, kernel 2.6.33.2 and xserver 
1.7.6 (with 1.8.0 xrandr is not working). My graphics chip is Intel i945GM.
-- 
Łukasz Maśko                                           GG:   2441498    _o)
Lukasz.Masko(at)ipipan.waw.pl                                           /\\
Registered Linux User #61028                                           _\_V
Ubuntu: staroafrykańskie słowo oznaczające "Nie umiem zainstalować Debiana"