Have you checked to see if both spray arms are clean and turning freely? The best way to check if they are moving is to set them so they are facing front to back or side to side. Start the program off and after it sounds like it has started to wash carefully open the door to see if the spray arms have moved fromm the postion you set them at.
The chances are that they have not moved and the most likely cause of this is the wash/circulation motor.