How to play over a local network?

Hi everyone. I have a problem specifically with the game when playing over a local network. My friend and I are in the same network segment, but we can't see each other in the local network. I downloaded the Lnagame1.1a software, entered our IP addresses, and now we can see each other. When I connect to him, it only lets me enter the chat, and then it immediately kicks me out with a message saying that the server has disconnected. After about 10 attempts, it finally connects, we select a castle, and start playing. We played one map for about 3 hours, but all subsequent attempts result in a disconnection after about 5 seconds, even when the connection is fully established. Sometimes, we can only get into the castle before the disconnection. We are playing Tribes of the East, version 3.0. Our network speed is 100 Mbps, and our external connection is 512 Kbps. We can play all other games without any problems using the same Lnagame software. Has anyone else experienced this with Heroes? Thank you.