blackhawk

Ok u guys helped me out by getting me to be able to host in Madden 06 with my router but it didnt solve my MAIN problem. In Madden 06 one player host the other joins, very simple. Apparently there is a trick to cause a "SYNC" error where the opponent causes u to disconnect therefor getting a loss. very anoyying but i was under the impression it could only be done BY THE HOST. but now that im hosting it continues to happen from people connecting.. at first i thought maybe they were just putting some kinda block on my ip or even closing a port but i dunno... my questions is what are they doing and how can i stop it?