Audio Delay?

Hey guys-

Every time I play a game for more than about an hour, the audio starts to delay. Audio doesn’t match up with what’s on screen. At first I thought it was just with Assassins Creed 2 after the patch, but I’m noticing that it’s happening in all my games. Does this happen to anybody else? I’m still under warranty, should I get it fixed? Or is there a way to fix it myself?