I am running the release version of Windows 7 and WMP12 (Windows Media Player 12).
I can see the UPnP service running on the DNS-321 in WMP however I cannot connect with the error "The remote media library did not allow the connection,  Please contact the device manufacturer for more information."  I can successfully connect to the UPnP service from my XBMC running on my Apple TV.  
I found a reference to the problem in the DNS-323 Forum, but no solution and no posts for quite a while.  I am starting a new thread here. 
Any suggestions/solutions?
References thread link below:
http://forums.dlink.com/index.php?topic=7307.0