Today, the sound on my Macbook just started repeatedly going off and on on it's own. The little gray and white sound icon that comes up in the middle of the screen when you adjust the sound is constantly appearing with the sound muting and then going back to normal. It is annoying to see and even more annoying to hear, especially when the sound keeps going out while I listen to music or watch a video. Sometimes it is hapening constantly back and forth and sometimes it will stop for 10 or 20 minutes and then start doing it again. I have tried restarting the computer but that didn't help. Also, for some reason a few of my preferences (time & date, airport settings) changed to default when I did that. Then I tried completely shutting down and restarting. Didn't work. Then I turned it off and left it for half an hour. Still didn't work. Can anyone help!? It would be greatly appreciated!

I just also discovered, the mute key is not working at all. And many of the keys are still typing but some of them act as the mute button also, changing the sound on and off. It's so annoying. Especially because it's doing it as I type this. Please, cam anyone help? My Macbook is no longer under warranty so I can't just replace it or take it in.