How do i fix the "disk is unreadable" error for one of my games for the Xbox360?

Now here is what i have determined so far. It is not the disk! So please don't give me advice on how to clean the disk or anything like that. The game runs fine when the hard drive is not in place. Although the hard drive has all my save data and new songs that i downloaded. The game also runs fine when i used the the hard drive cache clearing code. (XX,LB,RB,XX). Although it will then ask for me to update the game and whenever i do update i then get that the disk is unreadable again. This all started happening after Microsoft sent me a new xbox after i received the RROD several weeks ago. Also i have also deleted all of the Rock band downloadable content and then tried to run the game with the update and it still refuses to work. Any serious advice besides contacting microsoft or cleaning the disk would be nice. Oh and when i dont apply the update then i am forced offline in xbox live and none of my downloaded content is in the game. One last thing, the game and xbox are from the US.