Hey Man, *** I got it to work****
I was having the same problem running the "Beta version", "can not connect" firewall detected. My solution was to uninstall and load the Limewire 4.9.37 version and it connected. ((I think it may be related the the java version, I loaded it before the reinstall )) I had my XP firewall off , Sygate firewall off checked my modem and the UPnp thing was enabled but it still would not work.

Below, gave me a good result but I still could not connect until I did the above:

11. Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?