We hope you didn't have any big Xbox Live plans on Monday, September 29, because Microsoft's Larry "Major Nelson" Hryb has posted a notice that the online service will be down for maintenance, potentially lasting all day.
“On Monday, 9/29/2008 from 12:01 AM PST for up to 24 hours, Xbox Live will be offline for maintenance,” Hryb writes. In addition to Xbox Live being down, you won't be able to access the "My Xbox" section of Xbox.com, and the Xbox forums will be in read-only mode. Do note that this downtime will not result in any new features once Live goes back up -- it's only intended to prepare the service for the big Xbox Dashboard re-launch set to happen later this year, that'll add new navigation features and as well the Microsoft Avatars.
Source:→ Yahoo News