Imaginary firewall ?
 

Windows XP Home
Only Firewall is XP. It is disabled.
1G Ram
Lots of HD Space
Cable
D-Link Wireless Router, WBR2310
Comcast Modem DPC2100 Series (Supplied by comcast)
Home
LW 4.10.9 Java 1.5.0_09
Comcast
Test Worked
One other computer is using my network. My computer is the host.
Have used LW for years.
Yes, firewall was detected.

1) The only software firewall is the one supplied with windows XP. It is disabled.

2) UPNP is enabled on the router, port forwarding had no effect.

3) The second computer, which also uses the same version of LW, goes through my router and modem as well, and has no problem with its connection, therefore leading me to believe that this is not a problem with the configuration of the router/modem.

Apparently LW is detecting a firewall that either doesn't exist, or resides with the router/modem and yet allows the secondary computer to connect despite mine being the host. I'm no expert, but one would think that if the problem lay within the m/r, it would affect both computers, not just mine.

Any suggestions or further information needed?

I'm having the same problem. :( Limewire worked fine on my old computer, but when I installed it on my new one it wouldn't connect. I figured it was Windows Firewall and went through all the steps to unblock the program. When that didn't work I turned off the firewall completely, but the brick wall is still there and I still can't connect. The test worked and I've tried uninstalling/reinstalling Limewire several times.

You Dlink is a firewall. It does dynamic NAT. You'll need to configure it to forward limewire ports to your PC's private IP address.