how to solve greyed out volume control

Good call.

As a slight variation on your recommendation ...

I have the "Pro Tools First" application installed.

In System Preferences > Sound > Output, "Pro Tools Aggregate I/O" was selected (though I have not used the Pro Tools First application in a quite a while, but I have used Logic Pro with my MOTU 8 Pre as sound output recently which is what I believe caused the system setting change).

Choosing "Headphone Port" (my headphones were plugged into the audio jack) un-greyed out the Sound icon.

Resetting PRAM didn't help me either ....

I have also tried the following suggested in this article

http://applehelpwriter.wordpress.com/tag/grayed-out/

Any other suggestions?

Out of curiosity, did you try Repairing permissions using Disk Utility before manually changing with chown?

I realize that wouldn't help with the re-linking, though.

I forgot to mention that I even changed the logic board due to a graphic chipset failure and the problem was already present before exchange.

I had the very same problem and your solution worked a treat, Thanks a lot

Mac OS 10.8.3 finally solved the problem for me.

I had this problem too, and it's solved after 2 PRAM reset. After the first one, nothing hapend, but it;s fixed afteher the 2 atempt. thx leroydouglas

work for me. thanks!!!!

Fixed it by connecting my headphones and then ejecting them. Thanks!

The steps suggested by Thicot01 solved my problem(no reboot required). Thanks a lot.

This is weird, but I used an Apple audio video cable and plugged it into the TV. I then unplugged it and I had my sound back. It was simple but it did the trick when nothing else would.

For me the solution was more simple.

>>Sound

>>Output

>>Click on Internal Speakers instead of Multi-Output device

THIS IS THE WINNING SOLUTION. TRIED ALL THE OTHERS ABOVE. DID THE TRICK. ETERNAL THANKS, HOMIE.

Repairing Permissions in Disk Utility solved this for me, when none of the other suggestions in this forum worked.

This works for me, thanks.