Did you set up a static IP before you Port Forwarded ??
Instructions on how to do so...
http://www.portforward.com/networking/static-xp.htm
Instructions to forward a port for your modem/router...
http://www.portforward.com/english/r...4/Limewire.htm
It sounds like something went wrong within these steps....
No-one can download from you whilst still behind the firewall as they cannot see you...