Ah yes, good old port forwarding on battle.net.

If you want to use port forwarding, I would suggest using the port triggering feature of your router, and trigger ports 6112 through 6119 for TCP and UDP. Also, make sure you are not using any software firewalls on your computer (like zonealarm or windows firewall).
If you have multiple people on your LAN all connected to battle.net, and all of you try to join a game that one of you hosted, it sometimes causes problems with people joining. In that case, I would suggest turning port triggering off, and intead use the DMZ to open your specific IP address while you are hosting. (make sure you disable the DMZ after you are done)

What router do you have?