If you've managed to buy Kinect then be wary not to run it before its official November 4th release date, alas you won't be able to connect to Xbox LIVE.
Microsoft has confirmed that some retailers have shipped Kinect peripherals and games before launch date and warned that trying to run those games will trigger a system update which would prevent the affected console from accessing Xbox LIVE temporarily.
"Due to a retailer error, a very small number of customers were shipped copies of a Kinect game ahead of launch," Microsoft said in an official statement. "Since Kinect does not launch until Nov. 4 in the United States, customers who insert the game into their console before then will be temporarily unable to access Xbox LIVE. The retailer is contacting affected individuals directly to warn them of this situation."
The ban doesn't seem to have been deliberate though. Apparently, trying to launch a Kinect game requires two system updates, one of which hasn't been released yet. Installing just one of the two updates leaves the system in an unintended intermediate state while it waits for the second update to be installed before being able to connect to Xbox LIVE again.
If you've already tried to run a Kinect game and aren't able to connect to XBL anymore, don't worry: worst case, you'll be able to install the required update by the 4th of November, 2010.