Win7 Ultimate, current on Windows Updates.
WMP/Quicktime/YouTube playback all work fine. Downloading the WMV of any video plays back fine. All combinations work with either speakers or my LifeChat headphones fine.
It is only the page-embedded Channel9 video playback that I have found a problem with (any Channel9 video). It starts off muted on its own and stays muted regardless of choosing Unmute from the menus.
I would appreciate insight or suggestions to try.