I'm having regular (several times a day) complete machine freezes in 12.04 that I wasn't experiencing in Natty. Can't move mouse or ssh in, sound goes into a short loop.
On a possibly-related note, I also regularly get notifications that I've had a system error (which is what sent me here), saying that there was a problem with my graphics driver. In syslog I see things like:
May 21 20:07:05 blam kernel: [ 52.938651] [drm:i915_hangcheck_elapsed] ERROR Hangcheck timer elapsed... GPU hung
May 21 20:07:05 blam kernel: [ 52.938655] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
May 21 20:07:05 blam kernel: [ 52.941793] [drm:i915_wait_request] ERROR i915_wait_request returns -11 (awaiting 1714550 at 1714548, next 1716521)
May 21 20:07:21 blam kernel: [ 68.558597] [drm:i915_hangcheck_elapsed] ERROR Hangcheck timer elapsed... GPU hung
Any hints on debugging this or advice on what to do would be appreciated.
Running on an Ivy Bridge machine (i7-3770K), integrated graphics.
Edit: Also, after the system completely freezes, I don't have any error messages or any indication of what the problem was, even after trying to sysrq while it was frozen.