I made an attempt at purchasing Microsoft Points, both through the console, and the internet. Both methods produced a typical MICROSOFT error: invalid. Initially I contacted Xbox representatives to try and enter the information in manually on their side, again card not valid.
Wanting to get to the bottom of this, I contacted the bank for my credit card. Their representative verified THERE WAS NOTHING WRONG WITH THE CARD - IT'S VALID. . . . it gets better.
From this point, I called XBOX on 3-way while my representative was on the phone, verified through my bank, but xbox still said there is something wrong with the card; btw, IT'S THE SAME CARD WHICH IS ON FILE AND I USED TO RENEW MY YEARLY MEMBERSHIP!!!
The XBOX Rep informed me there was nothing to do but try another card! Why? It's the same VALIDIFIED card they have on file.