I am new to XBOX Live. I just received an e-mail telling me that I can get 2 months of XBOX live for $2, so I wanted to take advantage of it. BUT....when I try to add my debit card (the only card I have), it keeps telling me that my card number is invalid. I have used this card for well over a year now and know there's nothing wrong with it. I even used it earlier today to pay some bills and have never had any problems. What's going on here?