Out of experience, I know exactly what you're talking about. That perfectly circular scratch is indeed from the Xbox 360. It happens if your Xbox 360 is physically moved while a disk is being played. It happened to me with Gears of War.
There's no way to fix it, you have to go out and buy a new disk. It *really* sucks.
Did you move your 360 while the game was in? It will scratch even if you're on the dashboard.
Also, don't put your 360 on any kind of wobbly surface, because that can most likely cause it to scratch like that.
Sorry, bro.
