Right out of the blue, my Macbook Pro decided to only let one channel play on my headphones. They work perfect on my iPod. I've tested them with iTunes and other programs to exclude a software error and yes, I made sure that the audio balance is even. What might be the problem here?? I remember bumping the Macbook Pro on the table by accident (it was inside my neoprane casing). But it must take more to break something inside it, right?