In the past I have had problems with the UPnP feature in LimeWire the cure to it is to reset your router. The way I did it was to unplug my computer from the router then disconnect the power from the router wait for 30sec or so then plug it back in then depress the reset button for 15sec. I have a Linksys router and these are the steps to reset it. You can look up your router on the net to find the steps to reset it.
You may want to portforward you router I do not have as much problems when running in portforward mode. The link below will take you to a site for portforwarding.
http://portforward.com/default.htm