I've had the same problem before. Lens was dirty, and needed to be cleaned. Took the 360 apart, pulled out, then took apart the disc drive and cleaned off the lens.
Dust seems to be a problem with the 360. If it gets built up in your system it can cause the 2 red lights(overheating) and the disc drive will have a hard time reading discs if it gets any build up of dust, as well.