There is a chance your router (according to dslreports) does not support UPnP which is a system where a program requests the router to open a port in its firewall temporarily whilst the program is open. The earlier releases of 2Wire 2701HG-B did not have UPnP support.

In this case, you might need to port forward your router. Generally when port forwarding, you first need to set up a static ip address, though I did not see them suggest this for your router at Portforward.com.

Your model: Port Forwarding Limewire on the 2wire 2701HG-B - PortForward.com, and portforward.com shows the LW 4 set-up directions, the LW 5 one is here (ie: LW's Tools -> Options -> Advanced -> Listening Ports.)

You can also test your ports with http://portforward.com/help/portcheck.htm but should have LW open when you do.