Sounds like the same issues i had, only it happened while playing crysis aswell.. (since i maxxed all settings)

It isnt a quad 9950 is it?

My had a hardware fault/corruption/whatever.. I had to return the whole computer since its built by a online site who does it nearly for free and gives me warranty.

I have NO idea how to test it but they had to change it.

How much of your CPU is beeing used?

Mine was always at 100% when i ran wow without moving, after a while the comp always shuted down.