hey bump this thread as i also have the same problem.

i understand now that only one CC is tied to one account. which explains why i couldn't add the same CC to my US account as i already have it tied to my SG account.

now i think i have to check with the bank if they blocked it as they maybe detected the card to be registered under 2 diff postcodes, and thought it was fraud.

bought MS points before this and renewed to GOLD, no problems whatsoever.

looks like i have to wait till my MC debit card activates for me to use it with my US account.

hmm...that's weird. other people have no problems purchasing things...so don't think there's a blocking issue from MS's side. I hope so at least.

Ah well..if indeed my CC is blocked by the bank..they would call me up soon. I tried purchasing from xbox.com with the same error - invalid credit card information, or something like tht.

aww man..hope they don't block because of the region thingy man...stupid MS if they do...