I think it's a tad more than 5, but the number is maybe in single digits...among those who will mention it in a forum, at least.
I have tried using GSpot to diagnose the problem, and it says everything is fine. Although I have noticed that the ffdshow audio encoder does not load up with the five Maza-encoded files that people have problems with. On my computer, there's actually a problem with the ffdshow included with the K-Lite pack because the audio encoder doesn't work at all, but updating it on...free-codecs I think...doesn't change the lack of sound on those five, it just uses the audio encoder for every other recording now. Playing with the audio settings so that mp3 decoding is active and etc. doesn't change the fact it doesn't load up. *shrug* Maybe there's something I'm too stupid to know about my computer which causes this...who knows.
It's definitely fine with mplayer and VLC, but the latter screws up a lot of other things in my system and the former is...well...actually not bad, so maybe I'll stick with that. :) But MPC is my preference for all media files these days, and I'd like to figure out how I can get sound on those five uncooperative recordings. (Maybe not so much this one, but still...)