I'm an SBS and Exchange novice, so please be gentle. :)
Just did a clean install of SBS 2003 and the attendant exchange. We've got 4 computers (plus the server) and 4 users. I've been using the wizards exclusively. I've added the 4 users and computers to AD, but I've only run the connect computer wizard on one machine (and the primary user) so far. The other computers are still connecting to the shared folders through a workgroup without logging into the domain. Everyone is still getting their email via the pop server at the ISP.
Long and short of it is I can't mount the information store. At least that's the error I'm getting. I'm getting lots of 9175 errors "The Microsoft Exchange Server computer is not available" with a few 8197 errors "Error initializing session for virtual machine" too. I checked and the POP3 connector, Info Store, Management and System Attendant services are all started.
I'm getting pop3 connector errors too, but I figured I'd worry about that after I managed to mount the store.
Just for kicks I ran eseutil /p which took all of 10 seconds since the store is empty.
I'm sure this is a novice error, but I haven't been able to google my way out of it.