Halo 3 Maps Not Loading?!?

Well, I brought my hard drive over to a friend's to record some of my film clips onto the computer, well anyways, I'm pretty sure I didn't damage it... But once I took it home, and started playing Halo 3, it would tell me that I failed to load content, on ANY map. Not just the heroic or legendary ones, every map, (Last resort, Guardian, etc..) And I can't even play campaign anymore, or watch videos in theater, because no matter what I do, it tells me that I failed to load content. And in matchmaking, since I "fail to load content", it sends me back to the lobby as soon as there is a match found! It's getting ridiculous! Well, I know that it's either a problem with my disc, or my hard drive, and my disc isn't even that scratched, and I treat my xbox fine so I don't know how it got damaged. I tried that X,X,LB,RB,X,X, thing on the hard drive, but that only helped for half an hour, and then it just goes back to normal. Well, anyways, If anyone knows how to fix it, PLEASE let me know.