On February 9, 2007, about 1430 Pacific standard time, a Schweizer SGS 2-3C glider, N2438W, collided with terrain near Jean, Nevada. The pilot was operating the glider under the provisions of 14 CFR Part 91. The commercial pilot sustained serious injuries; the glider sustained substantial damage. The local personal flight was departing. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot submitted a written report. He arrived at the launch site about 1030, and set up a winch and cable ground launch system. He spent about 1.5 hours inspecting, removing, and repairing the winch cable. About 1200, he launched to the east on a normal climb, and released at 1,400 feet agl. He made a 5-minute flight and landed. The pilot moved the cable and winch to set up for a launch to the west. He requested a 65 mph cable speed; he cleared the pattern and midfield from both ends via radio. The takeoff was normal to 700 feet agl. The glider entered a thermal, and experienced a strong surge in rate of climb. The airspeed decreased to 50 mph, and then to 44 mph. He requested more speed, but he did not see an airspeed increase. He dove the glider to 60 mph, and requested more speed again. He noticed the airspeed getting slower despite a nose down attitude, which he assumed was from the cable weight with no cable forward pull. As the pilot made a third request for an increase in winch speed, he simultaneously pushed the nose down, and pulled the cable release. He did not hear a click, so he assumed that the cable had already back released. Looking forward, he noticed that he was getting very close to the winch and parked vehicles. His altitude was now below 400 feet agl; he elected to turn away for a downwind landing. He turned away, and was perpendicular to the winch. He saw his shadow on the ground, and was surprised and alarmed to see that the winch was still attached to the underside of glider. He pulled the release again, but the cable became taught. He felt no release, and the cable was pulling the glider quickly toward the ground. The control responses decreased. He unsuccessfully attempted to dive, and build enough airspeed to break the cable's weak link. The nose responded momentarily when he pulled back on the control stick. He thought that he detected a very brief forward motion rather than down motion. However, the glider hit the ground hard at a steep vertical angle. The pilot surmised that the tow hook jammed sideways.