At about 15:00 central time, the pilot of a Bellanca 7KCAB experienced a loss of control during the landing roll at Peter Prince Field Airport. The pilot and passenger were not injured. The pilot said they were approaching with light and variable winds when he noted the ball was full left with no rudder input. He went around twice trying to figure out why the airplane was not flying as it should. During the third approach he had full left rudder pedal input and nearly full left aileron inputs applied and was, able to keep wings level and fly fairly straight down the runway. He performed a wheel landing and when the tailwheel touched the ground the airplane immediately swerved to the right and groundlooped. Examination revealed the left rudder cable was off the pulley, leaving the rudder control surface and the tailwheel free to move.