When I try to turn up the volume, the megaphone icon is grayed out and there is a circle with a line through it at the bottom...like one of those cancel sign things. The bars are up to the end though. The bar is at the top when I click the megaphone on the top right of the screen too. When I go to Sound in system preferences it doesn't allow me to manipulate the Output Volume bar or click the Mute box even though the bar is still shown all the way to the right, and the Mute box is still unchecked. WTF HAPPENED. edit: Seems I've just realized there's a red light inside my headphone jack too. ???