This started the other day when I had my computer system at a clients facility to do a project. I noticed that while I was exporting (from motion headed to final cut) out videos, my screens would go black, and computer was non responsive (no com-opt-esc). Computer fans and light was still on, but basically nothing. fix was to hard boot, then repair permissions and such, then it would work for several times, then the same thing.
Of course I blamed the facility, I was using their monitors, power etc, I only brought the octo-core.
But it just happened to me a few minutes ago at home. I've exported several segments since I got it back home, but then the problem again.