I just bought my WD today, updated it to the newest firmware and tried to test it on some movies. It is generally ok, EXCEPT the following problem:
My video files are generally either avi files with srt subtitles, or mkv files with idx subtitles. With the srt subtitles no problem. If however I try to play an mkv movie with idx subtitles and I choose to display them, the screen goes black or white and no video is shown, UNTIL the first subtitle of the movie is displayed. From that point on everything functions ok. I have not tested it yet with pgs subtitles.
Most probably it is a bug, so I am reporting it in order to be solved as soon as possible.