On September 15, 2004, at 1045 central daylight time, a Cessna 172RG, N948SM, registered to and operated by the private pilot, collided with a taxiway light following a collapse of the landing gear at Montgomery Regional - Dannelly Field, Montgomery, Alabama. The personal flight was operated under the provisions of Title 14 CFR Part 91 with an instrument flight plan filed but not activated. Visual meteorological conditions prevailed. The private pilot reported no injuries, and the airplane sustained substantial damage. The flight departed George Downer Airport, Aliceville, Alabama, about 1000 on September 15, 2004. The flight was en route to Craig Field, Selma, Alabama, under visual flight rules. The pilot reported that, while in cruise flight approximately 15 minutes into the flight, he heard and felt a "thud" and detected an odor of "hydraulic fluid burning." The pilot elected to divert to Montgomery Regional - Dannelly Field. The pilot stated he attempted to lower the landing gear using the gear lever, and he heard noise and felt vibrations but he could not see the main wheels. The pilot stated he cycled the gear lever, and the circuit breaker popped out. The pilot stated he waited a few minutes, reset the circuit breaker, and the "amp gauge showed a total discharge and the low voltage light came on," and the circuit breaker immediately popped out again. The pilot stated he then followed the emergency gear extension procedures, but the circuit breaker would not stay in. He stated he placed the gear lever down, extended the emergency pump handle, and pumped 30 to 40 times but felt no pressure on the lever. A Montgomery tower controller verified to the pilot the landing gear did not appear completely down. The pilot executed a landing on runway 10, and all wheels collapsed beneath the airplane. The pilot stated the airplane touched down tail-low on the runway, slid on its belly down the runway for approximately 100 to 150 feet, then it jerked abruptly to the left, struck a taxiway light, and spun around in the grass. Examination of the airplane revealed the landing gear was collapsed, and the right wing spar and the right side of the elevator were damaged. The airplane was placed on jacks by maintenance personnel, and the landing gear did not function when both normal and emergency procedures were performed. The landing gear hydraulic system was found depleted of fluid. A hydraulic line on the nose gear actuator was found separated from its swedge fitting. Examination of the line revealed no evidence of abnormal wear. A review of Service Difficulty Reports on file with the Federal Aviation Administration for Cessna 172RGs revealed one similar event reported in 2001 in which a hydraulic line on the nose gear actuator was found separated from its swedge fitting.