I had this same problem in RVS we found though that you could change the port it connected on to fix the problem. however i have been unable to find the config file in this game to see how or where to change it.

Does anyone know how to do this in the config file and which config file to do it to?

The solution is, the reason why PB detects a duplicate is you may have installed the exact same thing on two computers in the same network. You must make a clean fresh install on the other computer. Both PCs must have their own copy of ET.

sorry if this took too long to be answered