This happened to me too. My computer always worked fine with my new LCD monitor, but I left the cables for it at my buddies house, so for the week Im stuck using my OLD 15" LCD monitor, and imediately after I plugged it in, I noticed purple fuzz in alot of places when browsing some websites and playing some games.
I also have no idea what its about, but I think it has something to do with the old monitor since it didnt do that with my new LCD.