The pilot reported that the aircraft was being landed with about a 10 kt crosswind from the left. After the landing gear was selected down, the pilot viewed the three green landing gear down and locked lights. The approach was normal with the crosswind being countered by flying left wing down. The left wheel contacted the ground first but the right main gear leg collapsed as it contacted the ground. The pilot lost directional control of the aircraft which slid to a halt about half way along the strip near the left side. Later inspection revealed that the lower forward lug on the bell crank assembly had failed resulting in the over-centre lock not being fully extended and the gear leg to collapse under the weight of the aircraft. The reason for the lug failure was not determined.