I had a similar problem after reloading the program file off-site into a PMC3 using tool box. If this sounds like something you did, make sure you download from system builder. If you are off site, select TCP as your connection and type in the home's external IP. As long as you have the right ports forwarded this should work.

Crestron's dynamic dns server took 8 hours to register the IP address before I could use my registered domain name.

Port 80 worked okay with my ISP