Why can't I purchase songs in Xbox Music?

My credit card information is saved within the Windows Live account, but when I go to purchase a song on the Lumia 625 it tells me to enter a credit card. I enter my credit card and it tells me I already have this type of card on file. Do you know what is causing this conflict?

Hi I have the same problem as of today. I updated my credit card info and now I can't buy songs in the music app. Did you figure out how to fix yours?