Xbox Live seems to be having an issue at the moment according to it Live status page which informs users that currently, making purchases are affected. Microsoft are aware of the issue and are in the process of looking for a solution. The rest of the network seems to operating normally, bar the Nat Geo App.
Purchase and Content Usage is Limited
Xbox on other devices
Buying downloadable items
Paying for downloadable items with a credit card
Paying for downloadable items with stored currency, adding additional stored currency, or viewing your balance
08/01/2014 18:05:08 GMT: