Volume stuck on maximum level, keys work but volume doesn't change

[aoisenshi]

I've had this problem before, but a simple restart has solved the problem in the past. My system volume is constantly at the maximum. It appears like I can control the volume with the volume keys on the keyboard or in sys prefs, but even when the volume slider is way at the bottom, it still sounds like it's at max. Volume control DOES work when output is my Internal Speakers (from my Mac Pro), but not when the output is my LED Cinema Display.

 

[GGJstudios]

Reset the NVRAM

 

[aoisenshi]

I should've known... Thanks.