80, normally. If you don't specify a port with a colon when connecting, as in "http://myserver.foo.com:8000", then you're definitely using the default (for HTTP) port of 80. If you use https, the default port is 443.
Most firewalls don't restrict outbound connections (from your desktop presumably, going out to the server). Do you know if you are using the default Windows firewall or if your IT is using something else to lock down your machine?
They are using something else. But after 3 reboots and letting the machine sit turned off for several hours, the problem seems to have resolved itself. Gotta love Windows Voodoo...
Thanks for the rapid response.