Problem working out the gameplay video

There was a problem hosting the game on other computers. We keep recieving this error everytime we try running it. We asked for help from other students doing this project that have already managed to run the game through lan, yet they cannot figure out why it crashes as well. I tried coming into uni again in the morning, and tried it again, and the same result comes up. Not really sure what to do now with the project.

I can get the map to work on UT3 when i solo, but multiplayer just doesn't seem to work at all.