I've been having trouble for over a year now of adding a payment method from the same bank (just different account)) or even a different bank. It seems any new payment method fails.
This time I got error code 8c320008. I tried adding the bank account info online and it said the payment method isn't valid, which I know it is.
I don't know what to do, but I would like to be able add bank accounts to purchase content and I'm just about done with trying to give Microsoft my money.