First thing that springs out at me is your WRT54G which was a lemon model that Linksys released. They never bothered to fix the firmware problems it has. Definitely Port Forwarding the device is better than UPnP for that model. It can't be both UPnP enabled & port forwarded, it should be one or the other afaik. Also for port forwarding the very first thing you must do is set up a static ip or else the process won't work & you'll need to delete that rule & re-do it. Double-check your port forwarding here PortForward.com - Free Help Setting up Your Router or Firewall

BTW there is a 3rd party firmware fix for that model router, but only do it if you are confident of such things. Check under UPnP for your Linksys model here: Connection problems? Check here first! (click on link) & you'll find it about half way down the page under notes about linksys upnp setting up.

As for your download issues, sound like fakes; check these tips: 1. How to find music, ____ 2. See http://www.gnutellaforums.com/showpo...45&postcount=2 (searching),
3. (a) Beware of Fake files in search results, __(b) Check this link Recognising fake files