i had this problem for the entire day, and im still trying to figure it out. i dont know what caused this to happen but every time i try to press the f10,f11, and f12 button for the volume it is not budging. it only shows a cancel sign at the bottom and the level is to the maximum volume. also, i tried clicking the icon on the desktop, that wont work either. then i went to sounds,and clicked on output. it shows it does not have a list and i cant click on the volume slide. NOTHING IS WORKING!!!. does this mean i wont ever be able to hear anything on this laptop? btw it is a macbook