This has happened three times in the last few hours. I've been listening to music on itunes, when the volume will gradually mute itself. It's as though I'm holding down the lower volume button on my keyboard but I'm not. I have a usb keyboard, so I move it out of the way to see my actual laptop keyboard, and there doesn't seem to be anything wrong with it. My keyboard wasn't pressing on the button or anything.
I can't raise the volume by just clicking the sound icon on the taskbar, I have to click the mute/unmute button on my laptops keyboard to turn the volume back on. If I don't when I try to use the sound icon, it will just scroll back to 0 sound as soon as I stop moving the slider.