Friend's computer consistently crashing completely about 1 hr into playing

[Totsy30]

I just got my friend to start BnS Friday night, and although he really likes playing the game, he is slightly put off by the constant complete computer crashes that this game is causing him to have. It happened a total of 3 times during our 5-6 hour session. We'd be playing normally, then he'd just all of a sudden go silent and his computer would shut off. Is this an issue that has been brought up before, and if so, is there a fix to it?