Yes, everything works fine if you install 7.5 AFTER you upgrade a clean 2k3 server to SP1.
The "firewall" had nothing to do with my bout with the new security model for files and services running on the server. Apparently it locks down service permissions, and in my case, trashed the registry entries for all of my PSA services. I had to remove all signs of PSA from the registry to get it to reinstall properly.
ClamAV, although it installs on its own, still cant get the service to start.
The MTA pickup event gets Error Code 5 when trying to execute, meaning it can't run an email through SA..
Since everything works right now, I am waiting till I get another server racked and restore into 7.5.