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.