Vern, I bet you didn't see this coming ...

[brell]

Computer: iMac 2,66 GHz Intel Core 2 Duo
Memory: 2 GB 1067 MHz DDR3
System: Mac OS X 10.6.8
Sound card: Internal Intel High Definition Audio

If 2 or more users are logged in and one of them (me) is running MM1 HD, then no sound whatsoever can be heard at other open accounts!

I tried to switch between users with MM1 HD on and off. If it is on then everything is silent at other accounts. If it is off the sound is restored.

[brell]

I forgot: The MM1 HD app has no effect on the sound at my account, i.e. the sound plays perfectly in my iTunes for example even if MM1 HD is on.

Also, this affects only sound output, not sound input.

[VernJensen]

Oh dear.

I can duplicate it. But not sure I can fix it. Sigh. I'll see what I can do.