Microsoft has issued a warning of an unfortunate problem that has been found with one of the features of the new dashboard update for the Xbox 360.
The update allows you to change the email account (Live ID) associated with your Xbox Live Gamertag, which is an incredibly welcome feature, and one that has been requested since the consoles launch.
Right now, however, if you go and change that email account you will in fact lose all of your forum posts, community user level, and icons earned at the Xbox.com forum. All posts made by your account will appear as ‘anonymous’. The team at Microsoft are working hard to resolve this issue as soon as possible, and we’ll let you know when this has been achieved.
Right now though, if you value your CUL, Icons, and Forum posts, do not change your Live ID. The fix should be here in a few days.
Source: Here
JUST DON'T CONNECT WITH XBOX LIVE AND DOWNLOAD THE UPDATE!!!!!!!
Edit: It slows the dashboard down and Xbox Live enabled games lag real hard!!! So keep the Xbox 360 off for a couple of days until they fix this update!