Questions

1) Are you also using an external cable or satellite box, or are you using the built in HD tuner of the Pannasonic HDTV?

2) What 'audio out' settings have you tried on the Panasonic? (e.g. PCM/etc.)

3) Are you aware that ARC functionality/compatibility is often best achieved by using components of the same brand, but even then doesn't always work well(?)