There is an Email on the Marketplace support:
Users may experience difficulties with the following services:
Buying downloadable items from the Xbox 360 console, Xbox.com, or Games for Windows – LIVE
A subset of users will experience intermittent issues performing transactions dependent on billing service availability including but not limited to: purchasing premium content, music, video, account management (renewal/recovery), linking Gamertags, and purchase/redemption of Microsoft Points. First time EA users and Games for Windows PC desktop client users will experience issues attempting to sign in to Xbox LIVE.
We are aware of the problem and are working to resolve the issue. We apologize for any inconvenience this may cause and thank you for your patience