Quick thought...I had a 7970 crashing in all sorts of interesting ways after 12.6/12.7. Hard crash w/ black screen and 100% fans, blue screen, pink screen, green screen. I reinstalled windows and a lot of other things to isolate the problems. A reversal to 12.4 helped out, and there was no more crashing. Just an idea for you to try...I hope it's not your' hardware! Good luck!