sbs 2000 to sbs2003 upgrade

After a sbs2000 upgrade to 2003sbs my exchange web acess is dead. Can't login pop imap or locally on server. info store is online - all permissions look good - get to web access screen - login works but web access hangs on the loading...inbox - totally stuck - need someone to remote in terminal services and fix it. as a 2003 MCSA, I'm stumped - ive reinstalled exchange-IIS and most of the OS, but still nothing.whats the fix