Note: ESPN2 still sounds awful. Crowd noise is sounds distorted and "digitally" - like a bad mp3 or a FM HD2 station that doesn't have enough bandwidth. It's only on ESPN2, no other channel that I have noticed.
I've noticed the audio garble, but I've also noticed it on other 720p channels. FoxNews, ABCFamily. I've never noticed it on a 1080i channel. Sometimes going to another channel helps, but usually a restart is required.
I have tried all suggestions - ESPN2 is still sounding bad. With or without DD5.1, it's the same. ESPN2 is the only channel, nothing else I have noticed. If you have an HD radio, it sounds likes a bad HD2 that needs more bandwidth. Crowd noise sounds very digitally.