It's strange because I've had Diablo III for a couple weeks now and I've been able to play it just fine without any performance problems. Starting today though, I've experienced some serious performance problems. I can play for at most a minute, during which time the computer will get hotter and louder, until the frame rate completely drops off the map and I'm forced to quit. It's a similar story with HD youtube videos.
I tried letting the computer just sit idle and cool down, but that doesn't seem to fix the problem. Only restarting seems to fix it, but that only gets me another minute of play time before I need to restart again.
Forgot to mention
It's a mid 2010 Macbook Pro 15" with 8 GB of ram