hmm. well. I reckon it's the registry hack that adds mp3 to windows media encoder's audio codec lists that is causing it.
Meanwhile, I'm finding that ffmpeg on linux is pretty effective for the encoding direct from a recording off miniDV. Seems to give better playback.. but I can't make the Z or my linux install of mplayer play back sound when I use vorbis for audio. ho hum. I'm sure I'll find it on google.