Does the other computer have LW also? Which version & does it connect?

If the answer is yes there is another computer that uses LW, then go to Tools -> Options -> Advanced -> Superreallyadvanced -> Firewalls. Check both the connection & listening ports of both LW's. Are either numbers the same? If yes, change the ones of the LW that does not connect. A port such as 64049 should be good to use.

You have Norton AntiVirus, does that include a firewall?