Audio Pop

I have a Mitsu 62825 connected to a  SA 8300HD via HDMI.  Recently a "static pop" has developed on the internal speakers when calling up the guide or changing channels on most, not all, HD channels.   The problem does not exist on most digital and analog channels, except coming initially from an HD channel, and does not exist on other input sources (e.g., coax or optical). I have tried three different 8300's and they all do it, but my neighbors with same cable set up, different TVs, don't have the problem.  Leads me to believe it's in the set, but strange it doesn't happen on 100% of the HD and digital channels.  Any thoughts? Thanks.