I've got a 20 inch iMac, purchased early last year (so just out of warranty!). I have it plugged into some powered external speakers, the Harman Kardon Soundstick IIs. It all worked fine for a year, but recently I have been getting really loud and harsh feedback/distortion. It seems to come randomly, including when the computer has been asleep all night (it is so loud that it wakes me up in my bedroom). The only way to stop it is to unplug the speakers. I think it is coming from the iMac, because when I've tried plugging the speakers into my iPod, I haven't had the problem (but I also haven't left it for long periods of time, so it wasn't at all thorough troubleshooting). It doesn't seem to be something like a loose connection, because twisting and jostling the cord when it is plugged into the iMac does not seem to affect the noise when it is happening, and I can't figure out how to trigger it. On the other hand, I frequently (a few times a day) unplug the speakers from the iMac, because they are very loud and that is the only way to turn them off and play something at low volume with no subwoofer). I have tried resetting the power manager on the iMac by unplugging it for 30 seconds, but that didn't seem to help. So: is this just annoying, or is it possibly damaging my iMac, and/or my speakers? Any suggestions on what to do? max P.S. my mastercard supposedly doubles the warranty on purchases, and that what i bought the iMac with: anybody have any experience with that?