I am using MC 20.044 at the moment but I have seen this kind of problem in the past too.
I started watching Sunday Night Football but I noticed that bitstreaming was enabled. I stopped the playback and disabled bitstreaming. When I restarted playing the program, the audio was all distorted. It sounds like it is playing at about 1/10 normal speed. I switched to 60 Minutes and saw the same effect. When I switched to a PBS recording of Foyle's War, there was no audio problem. There was also no audio problem when I played back a music file.
It seems to me that the obvious difference is that the first two files are using surround sound and the second two are probably just stereo files. I switched back to bitstreaming and the distortion disappeared. I checked DSP effects and I don't think I have enabled anything there. The number of channels is "same as source" and I am not doing any sample rate conversion.