.undf Codec How To Play Mkv Files On A Macbook?

How to play mkv files on a macbook? - .undf codec

I installed VLC, MPlayer OSX, DivX and connectors, including Perian for QuickTime. But nothing seems to play my MKV file. S Here's the problem:

VLC Player: Plays video but no sound at all, and displays a message stating that "UNDP supports VLC no audio or video codec"

MPlayer: Frost Fair. Open the file.
Quicktime: display subtitles, but no audio or video
DivX: freezes.

Can someone tell me where to play the files on my laptop. I have Mac OS X 10.5.5 ... Please tell me .... please please please!