For whatever reason, when I plug in my earbuds into the audio out jack of my PowerBook, I only get sound out of one earbud. The earbuds work perfectly with my iPod. For what it's worth, my iMac G5 experienced similar issues, but the problem went away after a software update. My 12" PowerBook G4 is a Rev. D and has all software updates installed. I'm pretty sure the issue (on both computers) began after installing iTunes 7.0 which leads me to believe it's a software issue. Any ideas? Thanks for your feedback.