Those who you spent all night and early morning playing may have encountered an error when logging in to Xbox Live. Worry not, the problem has been resolved. It was simply because of a firmware update to get Xbox 360s suited up for the coming Facebook, Twitter, and LastFM services.
Unfortunately, if you're looking for a changelog, there isn't one. The firmware update, as I've said, simply prepares your system for the coming features, but there's still no sign of any of those on your dashboard just yet. Those features will be arriving later this year.
Previous system maintenance: