The SpaceX Falcon9 launch vehicle was succesfully testet at the launch platform at Cape Canaveral.

The countdown was first stopped at T -2seconds due to a problem that turned out to be just a communication glitch

The problem was pretty simple: our autostart sequence didn't issue the command to actuate (trigger) the ground side isolation valve to open. The ground side isolation valve releases ground-supplied high pressure helium to start the first stage engine turbopumps spinning at several thousand rpm. That generates enough pressure to start the gas generator, which is a small rocket engine that powers the turbopump. There are no vehicle side valves actuated for spin start (just check valves), so it is an all engines or none situation.

Further testing has been halted due to extreme wheather in the area, but the vehicle remains at the launch platform

Source: SpaceX