going out on a limb here, but is your video track enabled/viewable? (in pro 1.5 there are 4 boxes by the track labels...on of those should be an eye. if you don't see that then the track is invisible)
and for exporting, are you encoding the export with lagarith or Huffy?
if so, premiere pro is notorious for sucking when it comes to exporting (only uncompressed rgb seems to work routinely)