This problem you are having is a fairly common problem and seems to be related to the latest Flash Player. The first thing I would try is to use the Flash removal tool if you haven't already and then reinstall Flash afterwards. This has worked for me in the past but it doesn't seem to work for everyone.
http://www.adobe.com/shockwave/download/alternates/
You may get lucky and get sound back by running Ccleaner and removing unneeded files and incorrect registry settings.
You may have to do some registry editing to fix this problem. Be sure to backup your registry or even set a System Restore checkpoint before trying to edit the registry.
Open the registry editor by clicking on Start, Run, typing in regedit and clicking Ok. Browse to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32
In the right pane right click and click on New, then select String value. Type in wavemapper and press Enter. Then right click the new key and select Modify. Type msacm32.drv and click Ok.
You can also copy and paste this text into notepad, save it with the file name fix.reg and then double click the file and allow it to be entered into the registry.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32]
"midimapper"="midimap.dll"
"msacm.imaadpcm"="imaadp32.acm"
"msacm.msadpcm"="msadp32.acm"
"msacm.msg711"="msg711.acm"
"msacm.msgsm610"="msgsm32.acm"
"msacm.trspch"="tssoft32.acm"
"vidc.cvid"="iccvid.dll"
"VIDC.I420"="i420vfw.dll"
"vidc.iv31"="ir32_32.dll"
"vidc.iv32"="ir32_32.dll"
"vidc.iv41"="ir41_32.ax"
"VIDC.IYUV"="iyuv_32.dll"
"vidc.mrle"="msrle32.dll"
"vidc.msvc"="msvidc32.dll"
"VIDC.YVYU"="msyuv.dll"
"wavemapper"="msacm32.drv"
"msacm.msg723"="msg723.acm"
"vidc.M263"="msh263.drv"
"vidc.M261"="msh261.drv"
"msacm.msaudio1"="msaud32.acm"
"msacm.sl_anet"="sl_anet.acm"
"msacm.iac2"="C:\\WINDOWS\\system32\\iac25_32. ax"
"vidc.iv50"="ir50_32.dll"
"wave"="wdmaud.drv"
"midi"="wdmaud.drv"
"mixer"="wdmaud.drv"
"VIDC.WMV3"="wmv9vcm.dll"
"VIDC.VP40"="vp4vfw.dll"
"msacm.voxacm160"="vct3216.acm"
"MSVideo"="vfwwdm32.dll"
"MSVideo8"="VfWWDM32.dll"
"wave1"="wdmaud.drv"
"midi1"="wdmaud.drv"
"mixer1"="wdmaud.drv"
"aux"="wdmaud.drv"
"vidc.VP70"="vp7vfw.dll"
"vidc.X264"="x264vfw.dll"
"VIDC.FPS1"="frapsvid.dll"
"vidc.VP60"="vp6vfw.dll"
"vidc.VP61"="vp6vfw.dll"
"vidc.VP62"="vp6vfw.dll"
"vidc.DIVX"="DivX.dll"
"VIDC.UYVY"="msyuv.dll"
"VIDC.YUY2"="msyuv.dll"
"VIDC.YVU9"="tsbyuv.dll"
"VIDC.DRAW"="DVIDEO.DLL"
"VIDC.YV12"="yv12vfw.dll"
"wave2"="wdmaud.drv"
"midi2"="wdmaud.drv"
"mixer2"="wdmaud.drv"
"aux1"="wdmaud.drv"
"wave3"="wdmaud.drv"
"midi3"="wdmaud.drv"
"mixer3"="wdmaud.drv"
"aux2"="wdmaud.drv"
"VIDC.MSUD"="msulvc05.dll"
"wave4"="wdmaud.drv"
"midi4"="wdmaud.drv"
"mixer4"="wdmaud.drv"
"aux3"="wdmaud.drv"
Some people have had luck using the K-Lite Codec Pack as described on this page.
http://wizkid.wordpress.com/2006/09/...io-on-youtube/
lycka till med fortsatt användande!
