I also can't find any info about your router supporting UPnP. It does have a NAT firewall though & this usually means that manual port forwarding's needed. Again though I can't find any info on how to set up port forwarding for your router You might need to contact Belkin's tech support for instructions
http://www.belkin.com/support/

Have you double checked your McAfee firewall settings?
http://www.limewire.com/english/content/firewalls.shtml

If this port 6346 test doesn't work http://www3.limewire.com:6346 then it means something's blocking LW's default port.

If your Norton AV includes the Internet Worm Protection, this can cause problems as seen here