My friend Ralph today ran into the issue described here:
http://blogs.msdn.com/jmacleod/archive/2008/06/25/iis7-sharepoint-2007-fails-with-503-service-unavailable-errors.aspx
I have set up MOSS on Win 2008 a few times and never run into this because I always turn IPV6 off in all NICs prior to installing MOSS.
-Michael