Keyboard Volume Controls Broken

I can't help, but I've suddenly got a problem on my Intel Mac Mini which at least merits the same description. I'm using the headphone output to external speakers. Up to very recently I could control the volume and turn mute on and off from the three keys above the numeric keypad section of my keyboard. Now this has stopped working: when I press one of these keys, I get the semi-transparent display of the speaker and the level of volume. Underneath that is a circle with a line through it (perhaps a 'mute' symbol) - but the volume up and down keys don't indicate changes in volume, and the sound itself is not affected. The Mute key shows the mute status (no "sound" lines coming out of the speaker icon), but no muting takes place. The volume up and down keys turn off the mute status display. The volume control on the toolbar at the top of the screen still works as normal. The only changes I know about are the recent security updates from Apple (all my Tiger software is up to date). Can anyone suggest any way of restoring these keys?

I had a system update the other day and am having the same problem. The volume controls across the board are not working. The system is on a constant MUTE. Adjusting the volume via the buttons shows all of the bars as full volume, but the "buster" symbol is below. Nothing. No pop noises either.

What's strange is that when I go to the preferences to change my alert sound - then it makes noise. So the problem isn't global, but isolated to the main audio.

If someone else thinks of a way out - please let me know, as I luckily haven't had a big multimedia project come in for now!

Thank you for your observation about the volume control in the menu bar. I am having a similar problem. My audio is muted, when I unmute the audio it stays unmuted, then if I increase the volume I get a sound and visual feedback but the audio immediately goes back down and is muted.

[I am thinking about taking my MacMini in to see what a Mac Genius has to say about it.]

Try zapping your PRAM. It worked for me!

I spoke too soon. The problem is still happening.

OK, this is embarrassing, but I'll go ahead and embarrass myself before the world! 8-) It happens I have a USB-based Logitech headset that has a volume control. The control happened to have something sitting on top of it. So when I was trying to do something at the keyboard the headset was fighting me. Check to be sure all of your volume controls are idle!

Same is happening to me after a safari update. Volume keys trigger the Screen visual, but nothing happens. i have to switch to internal speakers and it works.

Try making a new user, if the sound works there then trash this file for the original user...

/Users/YourUserName/Library/Preferences/com.apple.finder.plist