Do you run a dedicated server on a seperate machine or do you run the server on the same client? I have two computers, one main and the other a server. I ran the dedicated server on the one PC and noticed that people join and then get immediately disconnected. I have a linksys firewall and i tried both port forwarding as well as placing the server in the DMZ and still no luck.
People are stating that they get illigite server and parse errors. But completely random. People last about 1 minute in the game before disconnected. If I connect though, I never get disconnected through the LAN.