I can give you the instruction for your router to Port Forward, but you said you had already tried that...But here they are anyway, see if they help...
http://www.portforward.com/english/r...S/Limewire.htm
I also found these instructions at the Port Forwarding site it's for the Scientific-Atlanta WebSTAR-DPR2320, I know it's not your model but you may be able to access yours if the set up is the same...
http://www.portforward.com/english/r...0/Limewire.htm