Have a 15 month old Panasonic 50" TH-50PX75U and have noticed a high-pitched hum/whine that seems to be triggered by whatever's shown on the display. Does not seem to be tied to the audio, as the hum/whine happens when muted; the hum/whine also occurs regardless of source (cable, DVD, etc.). On DVDs or shows where the movie cuts back and forth between two scenes, the TV will repeatedly hum/whine on the one scene but not the other. Anyone seen/experienced this type of issue before? What causes it? Any way to address/fix? What's Panasonic like to deal with if warranty is expired?