Hmmm, ok. I ran a cpu vs. cpu match twice in a row on it and there wasn't lag at all. There was one moment of lag but I assume it was because of Fraps running. It wasn't recording either, I just used it to watch the fps. Funny how when it lagged, fraps still said 56 fps.
If that one game gets progressively worse, I wonder if some part of it is the programming of that particular game, because I don't know of any of the other games doing this.