If UPnP's not working, double check the way that you set up port forwarding. those portforward.com guides are normally really good. Did you set up a static IP first? Otherwise p/f won't work. Did you make sure to 'save & reboot' if that's part of your router's instructions? If you're using p/f now rather than UPnP, restart LW...see if the wall goes away.
Remember that the listening port & port you've forwarded have to be the same number.