Due to a wrong handling of a certain DirectShow ActiveX filter
WindowsMediaPlayer 9,10,11 can show (at least) one of these symptoms:
1.speeding up/or freezing the video playback when playing
2.missing sound when playing some audio in Mono

to correct this issue:
1. Open a DOS box and type (ATTENTION case sensitive):
Rundll32 Ac3Dx.ax, config
exactly as shown here, hit enter
SUPER(C) needs to be installed, otherwise the Ac3Dx.ax will be missing!


A window will open,
go to "system" Tab
Uncheck PCM
Uncheck MPEG Audio
Hit OK



close what you have opended
That's all