We were made aware of a widespread issue facing owners of Zune 30 devices this morning. We have a technical team working hard to isolate the issue right now and will update everyone as much as possible. Thanks for your patience while we get to the bottom of this.
The Zune support site also has a message noting Microsoft is aware of the outage.
Customers with 30gb Zune devices may experience issues when booting their Zune hardware. We're aware of the problem and are working to correct it. The Zune Social might be slow or inaccessible. Sorry for the inconvenience, and thanks for your patience!
Many are guessing that the error has something to do with the clock function on the Zune 30GB. CNN also has a story on the Zune failure. Hopefully, Microsoft will figure out the problem soon so people can get their Zunes back up and running.
Update 1-1-09: A solution to the 30GB Zune error has been posted. Microsoft says the error will resolve itself and it was a clock-related error.
Widespread problems with 30GB Zunes freezing up is being reported by 
