I'm afraid I'm another person who had huge problems resolving my inability to host games.  I've got a netgear ADSL modem-router (DG834GT).  I port-forwarded, disabled the plug and play settings, set up my PC on a fixed internal IP address from the router, ran CCleaner and Adaware and it all now seems to work.  Feel free to PM me if you want further details on my settings.  Thanks to those who posted guides and answered my repeated requests in the forum to try and enter games that I'd hosted to test.

I'm having a load of fun with this game.  I confess that I'm puzzled by the dev's suggesting on one hand that the graphics were restrained to permit the largest possible audience and on the other devising a system which will deter a very large percentage from playing the game online.  My impressions are a rather large number of people are having problems hosting games.