WDTV and Plex Media Server ( Browse error. Content not available )

I currently have the WD TV Streaming Media Player, running the latest firmware. I have a DLINK ShareCenter NAS which has all the movies.

Some of the the MKV files will work and some of the will not.I get the error “Browse error. Content not available”
when attempting to play these files. However, I have tried to play .MP4 files and .AVI files and it works properly.

But when I access directly thru Windows Share it will play without any problem.

Try to compare the media info of working files and unplayable files. .MP4 and .AVI are containers that use different codecs; some of them could be incompatible with your media server.