On November 25, 2003, at 1700 eastern standard time, a Cessna 560XL, N632QS, registered to and operated by Netjets Sales Inc., landed gear-up at Savannah International Airport, Savannah, Georgia. The Non-Scheduled passenger flight was conducted under the provisions of Title 14 Part 135 with an instrument flight plan filed. The captain, first officer, and two passengers were not injured. The airplane sustained minor damage. The flight departed Palwaukee Municipal Airport, Chicago, Illinois on November 25, 2003 at 1318 central standard time. According to the captain, the purpose of the flight was a cross-country from Palwaukee, Illinois to Hilton Head, South Carolina. The flight was uneventful until final approach to land on runway 21 at the destination airport. After completing the landing checklist the captain observed the main landing gear position indicator lights were illuminated indicating that the main landing gear was down and locked. The nose gear position indicator light was illuminated indicating that the nose gear was unlocked, and the hydraulic system was still operating. The captain aborted the approach, and executed a go-around. During the go-around the hydraulic caution lights illuminated. The captain contacted the Beaufort approach to advise them of the situation. The captain then requested to fly-by the Beaufort control tower to visually confirm the nose landing gear position. The control tower confirmed the main landing gear was extended and the nose gear was retracted. The captain declared an emergency, and was given radar vectors to Savannah International Airport, where an emergency landing on runway 9 was performed. Post-examination of the airplane revealed, the nose wheel doors were scraped and the nose wheel tire was blown. The pilot did not report any flight control malfunctions. A total of eighteen laboratory physical tests, a kinematic study, several general inspections, and a conformity check were conducted in an effort to duplicate the condition that occurred on 560-5132. Seven tests were preformed on a nose gear assembly from a Cessna test article. Eleven tests were performed on the nose ear assembly from 560-5132, including leak tests and service procedure tests. During the laboratory environment test the field failure could not be duplicated.