Firstly, I'm not *absolutely* sure of this so someone please contradict me if necessary :
Freeserve are not an ISP anymore, but a Service Provider. What this means is that they do not actually connect your machine to the Internet in the ISP sense. They do allow you to access web content, but since your machine does not have an Internet-valid IP address and is fed its content by their proxy servers, you're not truly on the web. This is the same case with AOL.
This has obvious consequences, such as no software dependent on true IP connectivity working... My reason for believing this (I don't have a Freeserve account) is that after much deliberation, it turned out that a client of mine couldn't connect to their office over VPN because her machine never was connected to the Internet per se. I just wish Freeserve would make that clear without charging customers 60p/min+ for their bl**dy "support" line.