Not again! NASA has postponed the final launch of the space shuttle Endeavour until sometime after May 10, spokesman Allard Buetel said Wednesday. Technicians are testing the electrical system to find out what caused the circuit to short out, which caused the originally scheduled April 29 liftoff to be delayed. The launch was put off at first until May 2, and then to happen no later than May 10 at 11:21 a.m., but now has been postponed again to an undetermined date. NASA repair crews have already replaced the power distribution box that shorted out a circuit supplying power to heaters for orbiter's hydraulics system. Representative Gabrielle Giffords (D-AZ), whose husband Mark Kelly is commanding the mission, left her rehab center and flew to Florida for the original April 29 launch. She is now back in Houston.