It appears that I can host games, but I cannot join ones already created. 

I followed the instructions in "the Monk's" PDF, but when i try to join a game, it still tells me that I need to open the ports.   I can create a game and it works when someone joins it.

Any suggestions??!

If you can host a game (and people can in fact join you) then you're set up the way you need to be.

The "message" you are referring to is pretty general and is probably being triggered because you've got WAN ping-response or IDENT blocked on your router (neither of which will stop you from hosting/joining).

thanks,

the Monk