Anyone got any ideas. I'm baffled. I don't think it's red October related as it started with 16.0.87 which was pre Red October. However builds previous to this were OK.
I have an idea... How are your Options -> Video -> Audio for Video settings configured? This was changed for build 87. It isn't quite part of Red October, but is part of the same "set" of changes.
In particular, what Connection type and Playback device are selected? Also, just for good measure, is VideoClock enabled?
The MKV file you listed isn't anything odd, and should probably be able to playback properly with Red October. I'm thinking something is borked in the bitstreaming settings. I'm really not sure, but if you have both:
Playback Device: same as audio
and
Connection type: Bitstream
I
think it might not work, depending on what you have selected in the Audio setup section. The basic idea of "same as audio" is that it wants to route everything through the Audio DSP, so that it can do room correction and whatnot on the audio output. But then you can't be bitstreaming, obviously, because the DSP needs decoded audio to do it's magic. So, for Bitstreaming, for now, I think you want to explicitly choose your audio output device as the Playback device in Audio for Video.
Otherwise, if this doesn't apply, and you still can't get it to work, try it with it set to PCM. You might have to hook up some headphones or something to the soundcard if you don't have any analog outs. But if that works, it could provide Matt et all with a nice clue to work on a fix.