I had this problem too. I use a D-Link DIR-655 router. If you have this
router (or perhaps a similar one), you can turn off a setting to fix
Log into your router.
Go to Advanced.
Go to Firewall Settings
At the bottom is: Application Level Gateway (ALG) Configuration
Uncheck the box marked (SIP)
You can go into the help files to read up on how this setting could be
causing audio troubles.
> Running windows messenger 2009 on vista64bit
> Using mark of the unicorn ultralite mkIII sound card.
> Messenger plays sounds and even recorded audio clips from others.
> But does not play sound in calls or video calls.
> Under audio setup the speaker setting is greyed out and I cannot choose my
> soundcard. It worked fine with the previous version of messenger.