Sometimes all of my audio output will mute. I don't know why and if I try to click on the un mute there will be a click and then it goes right back to mute. It also shows a white speaker on my desktop when this happens.

I have a USB headset from plantronics hooked up and the internal speaker but no other audio devices are connected.

The only way I can seem to get it to work again is to re-boot.

Have I got something set wrong? Or is there a problem? It will only happen randomly.

This morning I turned on the iMac and looked at the internet then went to take a shower. When I came back I had the problem. I had not used any audio devices this morning.

Thanks for any help or suggestions.