OldDeath - You solved it! I had to also set up port forwarding on my DSL modem to my wireless router IP address, in addition to the port forwarding from my wireless router to my computer IP.

Perhaps someone should make this clearer in the Shareaza FirewallGuide Wiki, because I would never have figured this out from there and I can't imagine my situation (a DSL modem with a wireless router) is uncommon.

Anyway, thanks a lot for your help!