I have the same problem as you.
With Windows 7, I am able to connect to my PC and see my media.
The music played fine, but the D-Link would lock up when trying to play a video.
Like you, I tried with differents videos that work with D-Link media server but no success with Media Player 12.
Please let me know, if anyone has successfully streamed XVID/DIVX .avi files from Media Player 12 to a DSM-320.