If UPnP is not working correctly, then forwarding a port is almost always more reliable. Go here http://portforward.com/routers.htm & look for Netgear & your model. Make sure you set up a static ip before you begin the forward process, else it won't work next time your ip changes.

BTW you should also check to see if there's any firmware upgrades for your model netgear. This can make a big difference in performance. But also check user feedback to be sure there's no bugs involved.