I've owned this unit for about 8 months. In the last 2 months, it's begun to make a popping sound when muting and unmuting, and also sometimes between chapters during a DVD (not skipping chapters, just letting the DVD play). It only occurs when the surround speakers are enabled.

I've gone round and round with Marantz and the service center. Last communication - this behavior is "not abnormal" (which made me laugh out loud - what does that mean?). I guess they don't want to say it's normal because that's perilously close to "they all do that," so they hedge their bets with "not abnormal" (which says to me that some units may do this, some may not).

I'm not done with these people yet - they aren't getting away without a fight.