I did not knock over or pick up the xbox while it was running. I stopped playing, got something to eat, and when I came back the game was unplayable. I opened the tray, and saw that there were several concentric lines dug into the disc. Doing some searching online, I find that this is ANOTHER problem of the xbox 360. Anyway, is there anyway to replace this disc through 2k? Im not up for purchasing another, even w/ the price drop.