On December 3, 1999, about 1430 eastern standard time, a Maule MX-7-160, N9235N, registered to Barry Aviation, Inc., operating as a Title 14 CFR Part 91 sailplane tow flight, crashed during towing climb from North Palm Beach County Airport, West Palm Beach, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The tow airplane received substantial damage and the sailplane, N2780Z released from the towline and was not damaged. The commercially-rated tow pilot was not injured. The flight originated about 14 minutes before the accident. According to the tow pilot, this was the second tow of the day for he and the glider pilot, and they were in towed climb at about 2,800 feet agl, when the sailplane abruptly pulled up and to the right, stalling the tow airplane. The tow airplane entered a spin, the tow and the sailplane both released their respective towline releases at about 1,200 feet agl, and during the three-turn spin, the tow's engine quit. The pilot recovered from the spin at about 700 feet agl, but did not have time to restart the engine. He performed a forced landing to swampy terrain overgrown with pine and palmetto. The tow pilot added that the first tow and release went uneventfully at 3,000 feet agl, and that both he and the glider pilot had previously conducted a positive release check of the towline and each airplane's hardware. It was the tow pilot who had conducted the glider pilot's mandatory dual checkout as a new customer, as well as his glider biennial flight review some months previously, and he felt confident that standard signals and procedures were in effect since the glider was not radio equipped. Additionally, the tow pilot stated, one day after the accident that the sailplane pilot admitted to him that he did not see the tow rope release before he started maneuvering the sailplane. The sailplane was inspected for release mechanism operation at the time of its return on December 3, 1999. No difficulties were noted then, nor have any difficulties been noted in at least 12 subsequent releases as of January 7, 2000. According to the sailplane pilot, at about 3,000 feet agl, the sailplane could not release and neither did the tow plane release. Repeated efforts by him to release were not successful until about 1,200 feet agl, at which time he did effect a release, and he proceeded back to North Palm Beach County, (F45) for an uneventful landing. He saw the tow airplane spin, lose power, and force land in the swamp area. According to FAR 91.309, (5), "The pilots of the towing aircraft and the glider [must] have agreed upon a general course of action, including takeoff and release signals, airspeeds, and emergency procedures for each pilot". The Soaring Society of America Private/Commercial Flight Manual states under the section titled, "Tow Release", the following: "When the [sailplane] pilot is ready, the release handle is pulled and the release confirmed visually. A level right turn is then made to clear the towline and towplane. This turn should never be made before release." The flight manual also states, under the section titled, "Aero Tow Emergencies-Sailplane Release Failure", the following: "If the sailplane's release mechanism fails, the sailplane pilot can signal by moving into a position where the sailplane can be seen easily by the tow pilot and then deliberately rocking the wings. After the sailplane pilot is sure the tow pilot has received the signal, the sailplane should be maneuvered into the proper high tow position for return to the gliderport. The tow pilot should release the sailplane at a safe altitude over the field. The sailplane can then maneuver to an unobstructed area on the airport. A higher-than-normal final approach should be planned to avoid snagging the towline". The tow pilot stated that he remembers selling a copy of the SSA flight manual referenced above to the sailplane pilot.