XBOX RROD 2 lights? but my XBOX isn't hot?

Ok, I turned my XBOX on and the fans got REALLY loud...and then I got the RROD with two lights on. So I turned it off and waited a little bit....When I turned it back on it worked fine and wasn't loud....but about 15-20 minutes into playing Call of Duty Modern Warfare 2, I get the RROD with two lights, saying it's overheating, but neither the XBOX or the power brick is hot. The power brick is warm, but it isn't hot, so I hung it up on a hook so it could get more air...that didn't work. Ok, I have a clean space, without anything around it, and my XBOX is in a well ventilated area. What is the deal? Oh, I also took my air compressor and blew dust out of the back fans and vacuumed the back too. And I thought it was the game, so I put in a movie, and I was able to watch it without any worries. Why would the game not work but the movie would? I really need help...how do I fix this?