I noticed this a few weeks ago, and I've had trouble in OS 9 with ALL sound going out, but I thought I'd write in to ask if it's a common problem or a known issue.
Left speaker is completely dead on my ibook. Plus I've got an occasional backlight cutout when I move the screen. I've got to send it in for that, anyway, but I can't do it over the holidays.
Just thought I'd ask.
Oh, it works fine in OS X, I just found out. It's only dead in OS 9 now.