Cannot Play Multi player

I have played WAW for about 2 months now and never had a problem,until recently. I decided to actually finish the solo game. Since then i have been unable to play Multiplayer Online. I get the message "disc unreadable"
"remove disk and clean with soft cloth". Tried this but no luck. Eventually after going to xbox live website and carrying out all the suggestions I took the disc back to the store and got a new one. Same scenario.
I am able to play online co-operative games ,split screen games ,system link games .but still not Multiplayer Online.
I made a call to Xbox live technical help line, after I told them my problem, I was told there system was down and could I call back later.phoned one hour later ,can you call back in two hours.called back two hours later, can i call back tomorrow. Called back following day, after explaining my problem technician said they would call me back.Guess what no one has 36 hours later.

Question Is my problem unique or are there other out there with this problem.? If you have had it, how was it resolved ?.
Answers or suggestions appreciated

Xbox Live intimated it may be a Treyarch problem and not Xbox Lives.!