So when I hit the volume keys the little volume display square comes up on the screen but there is a little circle with a slash through it at the bottom of the square and I cannot control the volume! When I go to the sound settings is system preferences the volume is un-manipulatable - same case in the menu bar - no control of volume. I know the sound works tho as I hear the startup sound when I restart the machine. Thoughts??
-Option-P-R keys when starting up and when you hear the bong chime 3 times let go and let it start all the up as normal.