Comment 4 for bug 440523

There is a full list at https://wiki.ubuntu.com/X/Troubleshooting/Freeze . /sys/kernel/debug/dri/0/i915* seems to be important. Strange that intel_gpu_dump doesn't return anything. I assume you are running it as root? You could try with xorg-edgers (https://launchpad.net/~xorg-edgers/+archive/ppa) since it in addition to bleeding edge drivers has a newer version of intel_gpu_dump.