updates:
– Finally figured out clip->modify->audio channels. Only it more completely kills the audio (no audio at all on either channel now).
– Transcoded, trimmed, adjusted, and compressed in FCP while waiting for some sort of answer or resolution. Not throwing that away any time soon.
– Adobe doesn’t appear to offer any help to people only running trials (even if they’re seriously considering a purchase of their flagship product – or at least were)
RESOLUTION: trashed everything CS6 related. Rebooted, disk util’d, and reinstalled. Now it all works fine.
Guess my install was hosed in some manner.