I'm running a Mac OS 10.2.6 behind a Linksys BEFSR41 router. In my sharing panel I've turned on Gnutella/Limewire in the Firewall tab, and in the router configuration, in Port Range Forwarding, I've enabled Ext.Port 6346 and checked the TCP and UDP Protocol buttons.

So I'm downloading alright on the main machine but when I try to download from my own server on another computer on another network, (a dial-up running OS 9.1, my server's on cable), I can see my search query go by in the main machine's Limewire monitor but I'm not able to make connection and download to the remote. Additionally, I see other queries for files that I have but I've yet to get my first upload.

What am I doing wrong?

Everything sounds right. I extended 6346 to add port 6347. I once read it's used for some kinds of connections.
Try entering the IP of the dialup connection in the connections pane on the G4, and vice versa. That might help

Are you on a static IP?

The bit about the uploads I can explain. Just because you have a file someone is searching for doesn't mean they'll choose to dl it from you. They can choose from quite possibly, hundreds of choices, and no doubt they choose from a fast one with a good rating. Perhaps because you've just gotten on, your rating hasn't been established yet.

The computer on the other network, dialup, let's call it the client, and the cable on the host, for simplicity. You said you configured the host router to let through 6346, but did you configure the client router to let through that? You said it was on another network, so I assume it has its own router as well somewhere in there. Also, does it have any software firewall of any sort?

Also, make sure you're using the most updated versions of LW.

Yeehaa! Its working! I took everything apart and put it back together again, and then left it running all night and this morning the monitor shows all kinds of activity. Thanks for the help guys!