Several people have been experiencing lag on Xbox live for the past few days why we aren't sure but it may have something to do with the fall update. Some of the problems that people are having is people getting kicked out of games, taking much longer than usual to join or get people into a game lobby, taking awhile ( or not eve accebting the chats with an error message) to accept chats and send messages and many others.
Major Nelson had posted that there will be Xbox Live Maintenance For the date of 11/13/07 If you don't know thats tomorrow.
Maintenance will begin at 0000 while the Xbox LIVE service maintenance will begin at 0100.
This is for maintenance only, there will be no new features that will appear on Xbox.com, your dashboard or Xbox Live when we return to service. It’s not time for the dashboard update…yet.