I believe the channel information in audio tracks with codec id A_MS/ACM aren't used correctly.
In the video I tested with all dialogue is only playing on the left speaker when using the 5.1 PCM track, the 5.1 DD track plays correctly. I checked VLC 2.1.0 on both Windows and Mac OS X.
Other players such as mplayer and MPC-HC play the audio correctly.
I uploaded a 10 second sample on http://streams.videolan.org/upload/ under the name "multichannel pcm bug.mkv".
Thank you for your great work.