On January 18, 2006, approximately 0800 central standard time, a Cessna 310N, N4196Q, piloted by an airline transport certificated pilot, was substantially damaged when the left main landing gear collapsed during landing roll at Destin, Florida. Visual meteorological conditions prevailed at the time of the accident, and an instrument flight rules (IFR) flight plan had been filed. The personal flight was being conducted under the provisions of Title 14 CFR Part 91. The pilot and 3 passengers on board the airplane were not injured. The cross-country flight originated In Griffin, Georgia, approximately 0730. The pilot stated that the flight had been uneventful. In preparation for landing, he lowered the landing gear and noted the three green DOWN AND LOCKED lights were illuminated. Shortly thereafter, he heard a "thump" which he thought originated from under the floor of the airplane. He then noted the nose landing gear light was still green, but the main gear lights had extinguished. The pilot proceeded with the landing and did not attempt to recycle the landing gear because he thought it might cause further damage. The pilot said that when the airplane touched down on runway 32, the right main landing gear light illuminated but the left indicator light remained unlit. He allowed the airplane to roll out and avoided braking and excessive steering inputs. About 200 feet from the taxiway turnoff, the left main landing gear collapsed. The left propeller struck the runway, stopping the engine, and the left wing and horizontal stabilizer also struck the runway. The airplane made a left sliding turn for about 150 feet before coming to a stop on the side of the runway. An employee of Miracle Strip Aviation, the fixed base operator at the airport, said that initially the landing gear appeared to be down. His attention was momentarily diverted and when he looked at the airplane again, the landing gear had collapsed. A post-accident examination by an A&P (airframe and powerplant) mechanic revealed the down limit switch, which operates the landing gear mechanical stop, had malfunctioned. The switch was found bent in the up position. According to the mechanic, the gear motor continued to run, causing the gearbox to over-travel and pull on the landing gear rods, retracting the landing gear.