I beleive not every gpu is fit for this exact algo/mining. For example: one of my 580s mines almost everything just fine - I tried it with lots of coins, and it's very stable. But when I run claymore's equihash miner - it also instantly crashes and pc reboots. Still it can mine all other coins AND equihash with other miners. It looks like hardware limitation.

So I think this type of issue could relate to other specific algos/miners. How much statistics do you have on cryptonight two threads mining?