Some .mov files noted as "unsupported"; why?

I am using the 2nd gen WD TV (firmware latest, but NOT bad 77 firmware) and notice that some of my many .mov files will not play and are designated as “unsupported” most of my other .mov files play just fine. They are all downloaded from the same source and so I am baffled as to why occassionally some are designated as “unsupported” Can anyone help me understand this and possibly what to do about it?

Happy New Year to all…

Still hoping for help on this topic. Thanks to anyone who has ideas.