Ashlyn
Just a note to say I was using a D-Link DI-604 router with latest firmware, and SmartFTP worked perfectly using UPnP (though it was quite slow with mapping/unmapping). I recently replaced my router with a D-Link DGL-4100 (latest firmware), and now SmartFTP (2.0.1000.4) won't work with UPnP. Resorting to PASV mode works as expected (which is what I used before anyway because the UPnP mapping/unmapping caused too much of a delay).