[Ctrl Alt Del]

Might be your console as well. Initially, the only game that used to freeze with the "disc error" warning on my 360 was Mass Effect, everything else went on quite smoothly. Later on, other games started showing this signs as well. After a month or so, I got the Ring of Death.

Now, I'm not sure you can ask for a replacement just yet, but you could/should try calling the 360 customers service.