[satelitko]

I've just stopped a five minute burn-in of FurMark, which is the most graphically intensive work this machine has done. Still no hang. I'm gonna try a Memtest and a HDD test, to disqualify them too. This is quite annoying

P.S.: It showed up on GPU-Z. Tops out @ 71C and stays there. Still no hang.
EDIT: OK, GPU-Z seems to be all over the place... now it stopped updating the temp @ 79C. Regardless - it doesn't hang even when GPU is stressed.
EDIT2: Currently running Memtest. Finally got gpu-z to work properly and it survived 5 minutes of extreme burn-in @83C stable.