It's actually not a port, it's what they call a HTTP HEADER named HTTP_REFERER. Some firewalls apparently are starting to strip it out for some reason (which is unfortunate in our case, because they are used for security to allow the message boards to make sure you're posting from a webpage inside the system and not spamming the boards through some kind of automated spam email-like thing.)
Here's a link to another site that uses our same message board software where they show how to address the problem in Norton's Internet Security/Firewall product:
http://www.roddingroundtable.com/dcforum/faqs/norton.html