I have an MP4 player that has an 8gb flash drive, that connects to my laptop through USB. That never comes up with autoplay, though I never had any use for it. Maybe autoplay isn't compatible with flash drives. To prove that though we need more people with the same problem.
If/when you had Vista, did autoplay work then?
Just checked autoplay control panel, flash drives are not listed. Only contents options and mixed data.