It looks like the problems plaguing Netflix, Last.FM and other services over the weekend are behind us, but there is still a bit of a headache on Xbox Live Marketplace. According to the Xbox Live Status page, there is currently a service alert for those that use the AppHub.
Users may experience difficulties with the following services:
• AppHub users creating a new account and choose an existing publisher name are not receiving a friendly message. Current work around is to choose a new name and try again.
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