Welcome to the Official BlackBerry® Support Community Forums. This is your resource to discuss support topics with your peers, and learn from each other. New to the forum? Please visit the ‘Getting Started’ link below.
As I understand it, the AC3 codec is not yet supported and that's the likely cause. You'd have to transcode those movies yourself using some other tool (I think Handbrake is often mentioned, though there's something else supposed to be easier to use).