It looks like Xbox Live is having a bit of an outage right now and Microsoft is working hard
to get the system back online. I would attribute this to the some 2 million people who picked up Halo 3
today but we haven't received confirmation of that (someone could have just kicked an outlet out of a wall). The outage seems to be localized to the web side of the service as I was able to play and send messages earlier this evening.
It looks like everything is now back and running