On August 5, 1998, approximately 1130 mountain daylight time, a Beech B36TC, N4BA, was substantially damaged during a wheels-up landing at Pinedale Airport, Pinedale, Wyoming. The commercial pilot, the sole occupant in the airplane, was not injured. The airplane was operated by Sublette Investment Co. Inc. under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local area personal flight which originated approximately one hour before the accident. No flight plan was filed. The pilot reported that he flew a "traffic pattern" for a landing and when he turned final, another airplane taxied onto the active runway in front of him. He aborted the landing and flew a "360 degree track" for another landing attempt. The pilot said that on his second landing attempt, he forgot to put the landing gear down. The left and right engine keels were bent, and a stringer and a rib were damaged.