So I went to take a screen shot a few seconds ago and got this horrific sound coming from my iMac, it lasted less than a second and. I figured out it's when I hold down Shift Option, then try to take a screenshot (Shift Apple 3). I don't hear it when the computers on Mute, so I assume it's some sort of sound issue. Does this happen to anyone else? I did a search but came up with nothing. Thanks, allison.