After researching the Flash Boards for awhile and gathering info, no
one (that I found) had a quick simple solution for a single button to
mute and toggle sound on and off for streaming sound. After gathering
bits and pieces from other posts, I came up with the following:

on (release) {
// Toggle a flag between TRUE and FALSE:
IamActive = not IamActive;

if (IamActive) {
// Mute sounds for "on" state of button
stopAllSounds();
} else {
// Override Mute for "off" state of button
myCurrentFrame = _currentframe
gotoAndPlay(myCurrentFrame);
}

}

I use streaming sound for synching movie parts to exact points of the
sound clip. I assign the above action script to a button. I found
that restarting the movie overrode the stopAllSounds, so using
gotoAndPlay and picking up at the current frame when the mouse was
released will turn the sound back on (thus making it look like a
toggle). The "IamActive if/else" script for the button is from
Macromedia.

Hope this helps some of you out there!