If you're going to have multiple machines on the same LAN on ICO at once, each needs to have its own port forwarded since you can only forward a given port to one IP. In the user.setting file (a search in explorer should turn it up), change the GameHostPort on one machine to 6113, and set forwarding on your router appropriately. You might also need to give it its own GameBroadcastPort as well (change one from 6000 to 6001).
