Is it possible to preserve Light Table (or Album) ordering when exporting from Aperture?
This always works for me as is in Aperture (v 3.1.2).

Are you pressing v to get to the browser view for the specific album or light table before exporting. You can drag things into manual order or specify any other sort like Date, Rating or other sorting. At that point when you export as versions, the counter takes the pictures in the order shown.

Here a pair of clips of Light Tables and the control for ordering.