Your lens may have scratched the disk. Check for a ring. Also, make sure you don't move or bump your console while it's on.
You can also avoid disc problems by installing your game, essentially making it digitally loaded (like DLC and all your XBLA games). Aside from finite HD space, installing your games is a better idea than otherwise.
Ou..outse..outsi...outside..is that how its said, did I get it right? Outside? what is Outside, is it something you eat?
I was able to play a scratched game by installing it. After it was scratched, no less. It was scratched when I got it. It worked perfectly, so I suggest you try that.