ON AUG 23,07 AT APPROX 4:30 P.M., I PULLED UP TO A STOP SIGN IN SAN MATEO, CA. I STOPPED COMPLETELY, MADE A RIGHT HAND TURN, AND PROCEEDED SOUTH AT APPROX 10MPH, WHEN SUDDENLY THE RIGHT FRONT END OF MY 2003 HUMMER DROPPED ONTO THE GROUND, AND I COMPLETELY LOST CONTROL OF THE VEHICLE. THERE WAS NO STEERING, LITTLE BRAKE PEDAL AND THE VEHICLE PROCEEDED TO TRAVEL TO THE RIGHT AND COLLIDED WITH A PARKED VEHICLE. THERE WAS ABSOLUTELY NOTHING I COULD DO TO PREVENT THIS. I EXITED THE VEHICLE, A PEDESTRIAN APPROACHED ME, AND SAID HE NOTICED THE WHEEL WOBBLING AND SUDDENLY FLY OFF, TURN AROUND, MY VEHICLE DROP, SCREECH AND CONTINUE IN A FORWARD MOTION, AND THE WHEEL TURNED AROUND, CONTINUED MOVING, AND PARKED ITSELF IN A GREEN ZONE, INSIDE OUT, NEXT TO A CURB. I EXITED THE VEHICLE, SHOCKED AND CONFUSED, INSPECTED THE DAMAGED VEHICLE, INSPECTED THE AXLE ASSEMBLY AND WHEEL SITTING NEXT TO THE CURB, GOT MY WITNESS INFO, TOOK PICTURES AND NOTIFIED THE POLICE. I ALSO NOTIFIED MY INSURANCE (AAA). I ACQUIRED A RENTAL VEHICLE AND WAITED TO HEAR THE OUTCOME FROM MY INSURANCE CARRIER. THEY HAVE SINCE NOTIFIED ME THAT IT HAS BEEN DETERMINED THAT I AM 100 PERCENT AT FAULT FOR THIS COLLISION AND PRINCIPALLY AT FAULT FOR A ROLLAWAY VEHICLE. I HAVE ALSO CONTACTED GMC , WHO ARE ADMITTING NO LIABILITY, (GMC SAID A REP WILL RESPOND IN 30 TO 45 DAYS). I AM APPEALING AAA'S DETERMINATION THAT I AM AT FAULT, DUE TO THE FACT THAT THIS IS A STEERING KNUCKLE FAILURE (SAFETY), I COULD HAVE BEEN KILLED OR