1. Did you set up a static ip first before you set up the port forward rule? Port forward rules are set upon the ip, so if it's a dynamic ip, the ip will continually change & the pf rule won't work. If you didnt' set up a static ip or did it after setting the rules, then you will need to delete all those rules & repeat them. Set up a static ip first
Setting up a static ip for XP
2. If you are using McAffee, you will need to disable your XP firewall via the control panel. Running 2 software firewalls causes side effect problems & less security not more. Double-check your McAffee firewall setting. Make sure it is set for clearance for limewire & gnutella.
3. Your model router is a "lemon" that Linksys released. They are a great company & have great products, but unfortunately that range of models had firmware problems which they never bothered to fix. There is a 3rd party firmware fix but it's not recommended for people who are not sure what they are doing as the danger of making mistakes is it could render the router unusable. As UKBob recommended, Port Forwarding generally helps make the router more reliable for p2p use, though still not 100%.
4. You can't always trust what ISP front desk people tell you. There was a report here
Telenor report of blocking but whether that is a blocking is not confirmed. And then
Connects sometimes via Telenor who also uses same ISP.