Looks like the time for the maintenance window has been changed:
MobileMe Launch
7/9/2008, 8pm-2am PT
As part of the MobileMe launch, www.mac.com will be taken offline at 8pm PT on Wednesday, July 9th.
Members will be unable to access www.mac.com or any .Mac services during this time with the exception of .Mac Mail accessed via a desktop application, iPhone, or iPod touch.
MobileMe will be available as soon as possible during this maintenance window.