Hmm, I found out a little more info. My ISP's connection analyzer tells me my modem, while NAT-capable, is in a mode that uses "IP passthrough", which I interpret to mean it is not using NAT [right?]. Does that mean the modem's firewall is not in the chain? My ISP's tech support lady says my modem doesn't even have a firewall but she doesn't sound very expert. In my Mac I have the Gnu/LW port open. In LW I have UPnP enabled and my listening port is in the recommended range. But I still have the brick wall icon in LW. I have not tried port forwarding yet. My IP address is dynamic, and they tell me it'd cost me $ to get a static IP.

Could my modem's firewall be what LW is sensing despite NAT being bypassed?

I can search and find, and can upload and download at good speed. As mentioned before my only complaint is poorer search results than I remember in days of yore. Is there any sense among the Gnutella community that there might be fewer folks on the network these days compared to, say, a few years ago?