Thanks Janusz, we're getting pretty close here. I have a single static IP address which is why I need to do some port forwarding - WWW at 80, FA at 8082, etc. I use zoneedit.com to handle all my DNS work. They have an option associated to web-forwarding called "cloaking" - you can find details at: http://www.zoneedit.com/doc/faq.html#faq36
Basically, as it redirects fa.example.com to www.example.com:8082 is "cloaks" the forwarding address and keeps fa.example.com in the browser. Anyways, that seems to be the problem. When I turn the cloaking off, everything works fine.
So, consider this problem solved as I'll just leave the cloaking off. I'm not sure if it's something you want to check into or test, as it seems to work fine in most areas of FA, but seems to struggle on the Company Setup screens.
Again, thanks for your help.