Just thought I'd add an update.

After the upgrade to Noteworthy, YouTube et al continue to turn the synthesizer volume down to zero. They must be nuts.

A few weeks ago, my computer had an icon of a gray speaker (very old fashioned in appearance). When double-clicked, that turned into the box with the slider controls. Slide up the synthesizer, and voila.

Since I upgraded Noteworthy, the gray icon no longer appears. Instead, I minimize the Master Volume box, (one level up from the slider bars) and it stays on my desktop. It does tend to diasppear at times, but that is the solution thus far. It certainly beats having to use System Restore.