Lose audio when Matroska is installed

[artki]

I install Matroska playback pack 0.5.exe. Installation seems normal. Thereafter, no matter what kind of video I play in BSPlayer I get no sound. MKV files will play - video only.
Video files play back normally on other media players - but the other ones I have won't play matroska.
Uninstall Matroska, sound comes back.
When Matroska is installed I look in the BSPlayers preferences menus to see if there is something I can adjust. Nothing makes the sound come back. When a MKV file is playing there's an extra icon in the system tray. No settings on that make any difference either.
I'm using the latest build of BSPlayer, the one from 16 sept. (.86 , 501)
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A little later...
I tried installed The Core Media Player as they claim to have better Matroska support. After installing it would play the MKV file - video, no audio. Just like BSPlayer. HOWEVER, then BSPlayer started playing the audio just fine! So BSPlayer must like the Matroska stuff installed with TCMP better than TCMP does!

Anyway, BSPlayer now plays the MKV files but it's all very weird to me.