I have a phantom 2 vision +. About a total of 20 flights. Yesterday I sucessfully had several good flights and on the last flight the phantom landed and tipped over backwards on the landing which was very gentle. It remained in that position until I disarmed the motors to stand it upright again. This took about 30 seconds. Was flying in GPS mode as a Phantom. Did not power the battery down and reboot. Rearmed the motors and advanced the throttle to lift off to about 4 feet. At that point the quad pitched back to about a 30 degrees and took off on its own at full throttle, arched over the roof of the house and at that point all I could do was pull back the whole way on the throttle since it was disappearing from view over the top of the house. The Phantom ended up stuck into the mud in the backyard with two broken propellers and the camera ripped right out of the gimbal. Took the quad inside and removed the gimbal, cleaned it up, reinstalled new propellers and flew it inside the house. Quad responds perfectly to the controls. Now I am stuck with a damaged gimbal and unknown damage to the camera. Can anyone shed some light on what might have happened? The quad flew perfectly before this incident!