What could be a very temporary glitch, we're seeing the Windows Phone Marketplace erring out for new downloads of apps. Numerous reports have just been sent in to us that users cannot download new apps to their Windows Phone.
Upon trying it ourselves, we repeated the error, listed as c101abb9, numerous times on a few devices.
We're not going to get too worked up about this as Microsoft could be updating some of those backend servers (and Saturday nights are probably lowest in traffic) or maybe it could be something bigger.
Update: Seems to be widespread as it is affecting Xbox 360 and some general LIVE services at the moment. Hotmail is working though.
Update 2: As of about 9:45pm EST, the Marketplace on our phone and others has started to work again
We'll keep an eye out but for now, if you're experiencing the same, you're not alone. Thanks, XboxOmac and Kalet B., for the tips