A few days ago, my 4 month old iBook 12" started to show the Sound icon on boot up, when it would race by itself, to max level and then stay there, making the "quacking" noise. Pressing F4 would then send the sound level bar racing the opposite direction to zero and then back up again. It's almost as if the key's stuck - but it isn't. Any ideas folks? I'm new to Macs, so be gentle with me please! :dummy: