I had the exact same problem. I noticed that it would function when I was downloading the same bittorrent on my computer. It appears to be getting data by my computer's bittorrent uping to it. It felt like a net problem so, I set the DNS-323's IP address to DMZ on my router, and it started working again. The DNS-323's app only mentions one port on the router, but my guess is that it's trying to use a port or range of ports we don't realize needs opening. I think D-link needs to give us more info about what's going on with this app. I can't leave my box DMZ'ed on a permanent basis. That would be crazy!
Note: I don't run my router in UPnP mode.
Regards,
Chris