The pilot of the tailwheel-equipped airplane reported he was performing a 3-point landing with a right 90° crosswind. During the landing, the tailwheel began to "shimmy." The pilot applied forward control stick pressure to reduce weight on the tailwheel and attempt to alleviate the shimmy but did not have enough airspeed to lift the tail and correct the shimmy. The pilot reported that as airspeed decayed, he applied full “aft stick” and full left rudder, but the airplane continued to drift to the right. In an attempt to prevent a runway excursion, the pilot applied the wheel brakes and the airplane nosed over. The airplane sustained substantial damage to the rudder and damage to the propeller, spinner and cowling. The pilot reported that postaccident examination of the tailwheel locking mechanism revealed that it was worn and would not lock to the right. Loose tail wheel attachment hardware was also noted. The condition of the tailwheel should have been checked during the last annual inspection; however, it is possible that the locking mechanism could have worn further during the 7 months between the most recent inspection and the accident flight. At the time of the accident the airplane was landing on runway 01 with wind 060° at 8 knots.