Unfortunately, after several months, I still haven't been able to track this issue down and I rarely use my surround sound due to the popping. I have tried unplugging all other electronic devices in the immediate vicinity and the speakers still pop. The one thing I did notice is that the popping never occurs until the system has been turned on for awhile (anywhere from 30-60 minutes) and then after that there are occasional loud pops that occur as one loud pop through all speakers. The vents are clear and the room is fairly cool, so I would be surprised if the receiver is overheating, but is there anything else that could build up after a period of usage in order to cause popping? This is a standalone home theater system (DVD player is seperate), the Panasonic SA-HT40, which I used for about a year before starting to experience this issue.