Does it do it when you play back an AVI or Quicktime it might be premiere is sampling the wrong field i am using on older version of premiere the way i fix that problem i Open the Capture window then clos it that usally fixes the problem.
Your jumpy video could be that premiere is confused about which FIELD it is sampling first, this sounds like a similar problem i have but my work around is to open the capture window then close it back and that usally fixes the problem.