I bought Just Cause 2 during the Steam Sale and have started playing it. I can play for like 5 minutes and it will freeze, go black, and then take me to Steam. It then says Just Cause 2 99% then finishes. I can launch the game again but it does the same thing

I am downloading Far Cry 3 right now, so could that have something to do with it?

Any help would be greatly appreciated