AFTER TOUCHDOWN ON RWY 11L WITH A WIND FROM 090 DEGREES AT 7 KTS, THE PLT LOST CONTROL OF THE ACFT. IT TRAVELLED OFF THE RT SIDE OF THE RWY & COLLIDED WITH A RWY MARKING SIGN. THE PLT FURTHER STATED THAT THE BRAKES LOCKED AFTER HE APPLIED THEM. EACH BRAKE ASSY WAS DISASSEMBLED WHICH REVEALED NO EVIDENCE OF FAILURE OR MALFUNCTION. THE TIRES WERE EXAMINED WHICH REVEALED NO FLAT SPOTS TO INDICATE THAT THE BRAKES WERE LOCKED.