How do you have the router set up (UPnP enabled if it supports UPnP, port forwarded or nothing)?
In LW go tools > options > advanced > firewall config & check if LW's listening port has changed...this can happen sometimes & can stuff up any port forwarding. If port forwarding is in place, log into the router & check all the config there.

Double check your XP firewall conifg.

I'm not sure if the 5100 supports UPnP, if it does & you haven't already tried, enable UPnP & then choose the UPnP option within that LW firewall config page. Apply to save a change.

Or you could try port forwarding if you haven't already, that should get rid of the firewall icon & hopefully help with your connection! Follow the directions here
http://www.portforward.com/english/r...0/Limewire.htm

Don't forget the step of setting up a static IP. LW's listening port & the port forwarded MUST be the same number.