ok guys and girls here it is:
I stumbled on this fix last night and it is very simple to do with windows xp and im sure the other operating systems have similar controls so here goes.
go to your control panel then go to add remove programs then to add or remove windows componets.then go to networking services.when you get there you will find a list of about six items and there will probably only be a check mark beside of one.i checked all of mine but that is up to you. make sure you check upnp user interface then click next then your computer will prompt you to insert your windows xp cd and the update will continue when you insert it and click ok.I use the linksys wrt54g router and wireless adapter.
my router nor my networking software enabled this for me this is something you have to do yourself.Since doing this i can connect in all aspects of the multiplayer options of the game that is in gamespy lan and direct ip before doing this i was not able most of the time to connect at all. Hope this helps i will keep checking a few times a day if anyone has any questions or you can feel free to email me at joey33570@hotmail.com in the subject line type help
good luck and good gaming