I just purchased my xbox a few days ago and made the decision to sign up for xbox live tonight. However, after I got the silver membership and tried to upgrade to the gold so that I could play online, it keeps telling me that my credit card number is invalid. But the strangest thing is that I used the same exact card to make a few purchases during the day. So I am rather perplexed as to why it would tell me that the number is invalid. Any suggestions would be much appreciated.