Look at your Bios settings, and just make sure you have all your software settings correct.
Did you try playing a game hosted on your own computer with bots? Could have been your connection lagging?
But yes, The problem COULD very well lead back to your PSU. If something happened to it, it could be supplying less power to the CPU or the mobo than it needs. If it gets less power it'll still run, just not as well as it should.
If your processor is at fault, however, I'll take it off your hands---try my luck with it