Why does Black Ops not work?

I pre-ordered Call of Duty: Black Ops from Amazon and just got it today. I played it on my month-old Xbox 360 S and did a bit of single-player. When I tried to go back to the main menu, my Xbox said the game was unreadable. I have tried to load it up several times and it has not gotten to the main menu. It has no scratches, and my Xbox is new, so what is the problem?