I don't think it's the OS any more, since there are no more errors. I am starting to think it's the power supplier. Even when running with power tune 15 and intensity 15 it shuts down after a few minutes when temps are around 50.
Seems to me that a 850W suppliers should support 2 cards drawing around 300W... Is there any app I can use to show how much power is drawn from the supplier?