THE PLT RPRTD THAT DURING THE LANDING, THE ACFT TOUCHED DOWN, THEN BECAME AIRBORNE. IT RESETTLED TO THE RWY AGAIN & POWER WAS REDUCED, THEN A SUDDEN GUST OF WIND FROM THE RIGHT RAISED THE RIGHT WING. THE PLT TRIED TO CORRECT WITH RIGHT RUDDER & AILERON CONTROL, BUT HE WAS UNABLE TO MAINTAIN CONTROL. SUBSEQUENTLY, THE ACFT VEERED OFF THE RWY & COLLIDED WITH A BERM. NO PREIMPACT MECHANICAL FAILURE OR MALFUNCTION WAS RPRTD. THE PLT RPRTD THE WIND WAS FROM 050 DEG AT 15 TO 20 KTS.