Just got off the phone with LG customer service. The rep told me to reset the tv (unplug for over a minute). I rolled my eyes but humored him... and it looks like it fixed the audio issue. We'll see if the problem comes back, I'll be interested to hear if it does anything for you guys. EDIT...

Same issue with my new LG 42LD520. Antenna placement seems to have an effect but I can't completely get rid of the audio dropouts on a few channels. Like FrugalTV, signal is high 60's and quality is 100. Hoping this isn't a firmware or hardware issue... I'll be interested to hear any solutions...