I want to think about that because it's just possible that you've cracked it.

I can't take the credit for it, someone else posted that elsewhere on the BBS and all I did was put two and two together (full volume, AC sensor switch, what things can wake the player after it's off). I forget who it was, but they flat-out said that waking up in the car could be a symptom of AC switch trouble. Was it Mark or Stu, or Rob S? I seem to recall it was someone with player-repairing experience.

The better test would be to check for the Dimmer setting.

Of course, if your player is blasting at max volume and draining your battery, you're probably more likely to yank the thing from the dash in a panic, but yeah, if you've got the presence of mind to turn down the volume and dig into the menus, that's a good test.