Just poking my head in to see whether anything had changed since I said my goodbyes to DLink UPnP. Doesn't look like it. I ended up running Twonky Media Server 4.4.11 on the DNS-323 without any problems. No refresh issues. Streams my 2300+ music files, as well as 5000+ JPEGs without complaint to my PS3. Updates the index in less than 2 minutes.
Not blaming the engineers at DLink for anything. Not being childish, either. I am an EE myself, so I know how things sometimes "work", or not, in R&D.
I blame DLink management, likely the Marketing Droids, for insisting to claim that the device is providing UPnP functionality, and particularly PS3 compatibility when all they allow R&D to deliver is some half-baked, homegrown solution. Other vendors choose to embed Twonky's solution into their devices. They know why.
But mostly, I blame myself for not having done my due dilligence before choosing the DNS-323. At least I was able to jump through a few hoops, spend some additional time and cash, and come up with a workable solution.