Many good ideas here, but I found the real problem and possibly the fix by accident.  Last Friday my computer crashed and  tech support had sympathy but little help.  Since I use my computer for business I needed to recover pronto so I bought a replacement. My old computer was 3.0 Mhz, 32bit, 4 GB RAM, 80GB HD, XPProfessional.  The new one is 2.7Mhz dual cores, 32Bit, 2 GB RAM, 500GB HD XP Professional.  Carbonite provided crashed files and after re-installing my progys I was amazed to find P8 dials operating very smoothly and normally (not jerking).  IMHO dual cores solved the jerky dials and two render threads really sped up IL renders.    Best wishes for happy holidays.