I've had some trouble with this myself, but I am able to host games just fine. However, when I try to join one of my friends servers I am unable to connect to it except on a blue moon. Funny thing is when I do the listserv command it shows her server, but when I actually go look for the server on the game it's not there. I even checked here and it shows that the server is still active and can still be reached. So, I tried to connect by typing the IP in and was still unable to get into her server. Maybe it is a glitch with the MS (highly unlikely, but possible?) or that her ports were bad, so I am not sure what it could be.
Also, Waffles, my router wasn't listed either, but I was able to forward my ports. To do that, go to command prompt and type in IPCONFIG. Write down the default gateway IP address and then open an internet browser (like Internet Explorer) type in http:// and your gateway's IP in the address bar. It should ask you for the username and password. Normally, the user would be Admin and the password would be either pass or password, unless they were changed. After that, you should be in your router's settings and there should be an option that says port forwarding where you can set up the ports for your computer's IP. That's how I did it, however.
