I've had the same problem with my door chime, and front driver door speaker not working also! usually after it rains, when the humidity is high, or it is under 65-70 degrees outside... weird I know. and I thought it was weird when I've read on other threads and posts on this site of other people mentioning the same thing, but there's actually some kinda weird truth in what I, and other people are saying about this.
I've also read that it could possibly stem from something wrong with the sound/radio amplifier, or the wiring harness(es) coming from it, to the speakers.
something that GM needs to address and fix, I think. I love jammin n rockin out on the way to work and lots of other times, but pisses me off that the sound system doesn't sound as good as it should (and previously had, up until last summer)....[/color] :angryfire: