FWIW, I got a copy of Premiere Pro working and it can indeed edit M2V files. It cannot import .AC3 audio files (though apparently can export them). I haven't quite figured it out yet, I need to do a bit more reading, but apparently it builds a 5.1 channel "submix" from other sound sources so if I split the .AC3 file I've got to 6 mono sound files I should be laughing, once I learn how to build the "submix".