I have a powermac G5 dual 1.8 running Tiger and I just lost all my sound.
The speakers work elsewhere. I also ran the hardware test but it doesn't appear to cover the sound card.
I was listening to music this morning and now nothing.
My sound card fried??
Is this a system wide problem, or just in iTunes? I take it you've gone into the Sound System Pref to make sure that the correct outputs are selected as the default sound output?
I have to ask the dumb question, is the sound muted?