hey, i just got in from work, where my powerbook G4 1.67Ghz, 15" was working perfectly fine...i open it to listen to some music, and the volume control doesn't work, as in, no volume control, no little popup telling me about the volume. if i press mute, it does stuff, but not what it's supposed to. i've been into sound properties, and i'm not able to control the volume from there either...the volume control bar is greyed out does anyone know what might be effecting me? i've not done a software update since itunes last week, and i'm really stuck as to what this could be. i've run the apple hardware test, and it's come back inconclusive. any help would be awesome!