4 x 333 is 1332 las tI checked :)
Try clearing the CMOS is always a good idea, then load optimized defaults, set disk boot order and other non MIT changes you have made before. Then set memory mulriplier and timings manually if not already set to correct speed (1333 max possible at 333MHz FSB).
Do you use Memtest86+ or Memtest86? Use Memtest86+, you can download the latest version from the programs sticky in the forum.
With all 4 slots populated +0.05 - +0.15 MCH OverVoltage may be needed.
BTW for 1333 1.5-1.6v may be enough can you post a screen capture of MemSet main and SPD windows?