I have had this problem on every 10.5.x Build, now running 10.5.8 and still have this problem. Toshiba Tecra A6.

I have a feeling it has something to do with the power management. I won't hear the pop until I activate a sound or screen saver/sleep!

Any in site would be greatly appreciated. I'm trying to run this laptop as a Keyboard midi controller with Ableton live.

Thanks!