you cannot really fix this, because the game is an xbox import.
i can also not play Garden and Graveyards, for example, together with my son.
if you want to play with 2 comps from the same network online you have to set both comps to a FIXED IP.
Problem here, most static(fixed) modes are not supported by routers.
other possibility is that you run one comp over a proxy connection, but that player will have some little delay ingame then.
like 0.5 seconds from clicking to the actual shot.
