The student helicopter pilot was preparing for his fourth scheduled solo flight, intending to depart on a local flight. The student reported that as he started to raise the helicopter’s collective, the helicopter started to slide to the right. He added that he stopped moving the collective and applied left cyclic, and the helicopter stopped moving. He then continued to raise the collective to begin his hover. The helicopter rolled-over to the right, and impacted the ground. The flight instructor who was watching the student, reported that he saw the helicopter move to the right about a foot, stop, and then as the helicopter started to lift, it “instantaneously, rolled to the right and struck the ground." After the accident, both the instructor and student stated that it appeared the helicopter’s skid may have gotten caught in a crack on the ramp’s cement surface.