Had a similar problem.
I have a drive on my WIn 2008R2 Server which I use to store all my mp3's.
Even though all the folders were correctly shared, the 83i still would not see the files. With my previous NAS (Synology CS-407e), I had no such problems and it drove me nuts.
It was only when I figured out that the 2008R2 server had no media server application unlike the Synology NAS. I installed and configured Twonky Server (even though not officially supported,it works fine) and after that the 83i automagically saw everything.
I don't know the D-Link 320, but I'd hazard a guess that it either does not have a DLNA media server (or something compatible) as part of its operating system or, if it has, it isn't switched on.
If there is no such beast, you might want to do some research on Google to see if anyone else has come up with a solution.