On May 23, 2005, about 2030 central daylight time, a Beech BE-58, N6654Y, registered to and operated by a private individual, as a Title 14 CFR Part 91 personal flight, had its landing gear collapse while landing at Gulfport-Biloxi International Airport, Gulfport, Mississippi. Visual meteorological conditions prevailed, and no flight plan was filed. The commercial-rated pilot was not injured, and the airplane incurred substantial damage. The flight originated in Baton Rouge, Louisiana, the same day, about 2000. The pilot stated that when he was cleared to land on runway 18 by the control tower, he extended the landing gear, set flaps to full, to reduce speed, rather than descend at an idle power setting. He said he observed three green landing gear light indications in the cockpit, and applied "slight" engine power during the landing flare and landed normally, or "slightly softer than normal". He said the airplane "rocked" slightly side to side, and when the airplane's full weight was on the main landing gear, the left main landing gear collapsed, followed by the right main landing gear. He said he then pulled back on the yoke, as the left propeller struck the ground. Moments later the nose gear collapsed, and the airplane slid about 400 to 500 feet on the runway, before coming to a full stop. He said there had been no significant prior problems, and a recent landing gear check had been conducted due to him having previously experienced slow landing gear extension, retraction, and noise. He said he thought the slow extension and noise had been corrected by lubrication since the landing gear's operation and speed of operation had returned to normal after 3 or 4 flights. During postaccident inspection, the pilot said he noted that the battery and alternator were off, the landing gear circuit breaker had popped, and the left gear had not fully retracted An FAA inspector responded to the scene and conducted an initial postaccident examination of the airplane. According to the inspector, there was "scraping" damage to the inboard landing gear doors, however the outer gear doors sustained no damage, and these items were consistent with the landing gear being extended when the airplane was too close to the runway surface in order for the gear to extend fully. An FAA licensed airframe and power plant mechanic performed postaccident maintenance to repair the landing gear. The mechanic stated that during the course of his maintenance he installed new Brace Assemblies (P/N 38-815125-12 and 38-815125-14), in accordance with the Beech maintenance manual, since the braces had been bent when the gear had folded. After installing the braces he said he then performed retract tests, and the landing gear system functioned normally. As he was moving the airplane with a tug, he said he noticed that the right landing gear was about to fold. According to the mechanic, when examined he found that the down lock mechanism had not pulled into place, and that the pulley, part number MS20219-2, was split on one side, allowing the cable to run into the split, making the downlock cable fall short of engagement. The mechanic said that the pulleys had to be removed to see the split, and that when he checked the left side, the same conditions existed. The mechanic replaced both pulleys and both downlock cables, which resolved the landing gear downlock problems. Examination of the airplane's logbook records show the airplane received a 100 hour and Annual inspection on July 31, 2004, about 70 flight hours before the accident. During this inspection the mechanic stated he performed a main landing gear retraction and emergency extension test.