Many users reporting problems
Users in multiple and different forums are complaining of issues with their Call of Duty: Modern Warfare 3 discs on the Xbox 360. Apparently, some users are having disc read errors. These errors can range from the disc not even being recognized when inserted into the drive tray, to “unable to read disc errors” that show up during various stages of game play.
According to those who have the issue, it does not seem to be a problem with a specific DVD drive in the Xbox 360 console because if you are having read issues with the disc in one console you will have the same sorts of problems in another console. This does suggest that the problem is with the disc, rather than the DVD drive in the console.
Microsoft support suggests that users having this problem seek a replacement disc. Some users have reported that they have had issues with the replacement copy, which could indicate that there might be more going on here.
So far, Activision has not offered any comment; but it is obvious that they know the reports of a problem exist. From what we know so far, they have yet to do anything to address the issue.