I see you already stated you had your DVD drive repaired. Unfortunately, the repair was performed by an unauthorized repair center that installed an unsupported DVD drive. The Xbox LIVE terms of use clearly states that you agree that you have not performed
an unathorized repair.
See Section 12 of the LIVE terms of use:
www.xbox.com/.../livetou
"You agree that you are using only authorized software and hardware to access the Service, that your software and hardware have not been modified in any unauthorized way (e.g., through unauthorized repairs, unauthorized upgrades, or unauthorized downloads),"