New problem with WMC

I've had an oddity show up a few days ago.......

When using Windows Media Center (Vista) the navigating sounds when moving around the WMC menus do not work. Once a recorded or live show is played, the sound starts to work fine, but then when it's done and goes back to the menus - no sound again.

This happens on both of my TVs, so those don't seem to be the problem. Plus the sounds work fine at the PC, and even if I leave the monitor on and go to the TVs to control them I can hear the menu sounds in the next room - just not at the TVs themselves.

Not sure if this is related, but this started happening at about the same time, but also when I hit Stop when watching a recorded show the screen goes black until I hit the "back" button and get back to the WMC show menu. This does not happen at the PC, just when using the remote at the TV.

I tried rebooting the machine, unplugging and plugging back in the ZvBox, and then unplugging the ZvBox and then rebooting the machine like in another forum suggestion. No go.

Would it make sense to try uninstalling the Zv software and reinstalling it? Or is something else at play here?