I have the same problem since a couple of days now, I load up the game and after about 5 minutes my computer crashes. I am also running and Radeon with 2 additional coolers. It never happened before. Help would be appreciated.
Try the fix proposed by Itokaru, then come back to us if you still have the problem. Also, the number of fan you have doesn't mean you can't experience overheating, if they are full of dust of malfunctioning you will still get overheating so when you experience crashes, looking for dust inside your computer always helps to rule out a few possible causes for the problem.