We've just been informed via Gamertag Radio
and Xbox.com's TriXie that the Fall Update is releasing with a minor bug related to the new Live ID switching feature. Specifically, when you download the Fall Update and change the Live ID you have associated with your gamertag, a bunch of Xbox.com issues arise. Problems including all your Xbox.com forum posts being deleted, your community user level will go bye-bye, your icons will be erased and your gamertag will be replaced with with an "anonymous" name. The Xbox 360 dashboard team is trying their darnedest to get a fix in place and should have a solution available in the next few days. Until then, DO NOT change your Live ID that is associated with your gamertag until a fix is announced. You've been warned.