My iMac's sound wont work. I hear the chime on start up, and that is all. I tried changing the volume with my remote, and the slider came up, but underneath it was a little circle with a slash through it. I went into system prefs, and it said that there were no output, and no input devices. I tried going to Audio MIDI Setup under utilities, but every option on there is grayed out, and it says Input is not supported, and Output is not supported. Please someone help me!!!