Going to need a bit more info here! Are you sure it's your modem firewall... I mean have you made sure that you're only running 1 software firewall & that it's configured properly? Have you been through this sticky?
Connection problems? Check here first!

Have you used these instructions
http://www.portforward.com/english/r...5/Limewire.htm
and did you make sure to set up a static IP address first? I've got a NetComm (different model) & I stuffed up royally the first time I tried to set up p/f... didn't click on "Save & reboot" after going through the steps. Did you click it?