I found this over on another forum. It doesn't work for recorded events, but has worked for me when having audio problems watching OTA live.
Menu>6>9
Scroll over and highlight the channel you're watching
Wait for the signal bar to be "locked"
Press "View Live TV"
My local ABC is doubly affected because when I do get audio, it's mono instead of 5.1. This won't fix that issue, but I can deal with mono sound compared to no sound at all.
I've tried all of the "workounds" and nothing gets my audio back on my CW. Thanks though.
S~