2002 CHEVROLET PRIZM Tires Problems

I INSTALLED FOUR KUMHO 795 TIRES (P185/65R14) ON 10/03/2006 ON MY 2002 CHEVROLET PRISM LSI. IN NOVEMBER 2008, WITHOUT ANY WARNING, ONE TIRE (FRONT PASSENGER SIDE) RUPTURED ON THE INSIDE SIDE WALL. I WAS LUCKY NOT DRIVING ON THE HIGHWAY. THE CAR ALMOST LOST CONTROL. I WENT TO THE DEALER (EXECUTIVE WHOLESALE TIRE, ROCKVILLE, MD) AND THE DEALER INSISTED I MUST HAVE HIT A POTHOLE. THIS TIRE WAS REPLACED WITH A KUMHO KR-21 FREE, SINCE KUMHO OFFERED THE ROAD HAZARD WARRANTY ON THE 795 TIRES. AFTER THIS TIRE WAS INSTALLED, THE TIRES WERE ROTATED. ANOTHER KUMHO 795 WAS ROTATED TO THE FRONT PASSENGER SIDE. LESS THAN A MONTH LATER, I NOTICED THAT TIRE IS LEAKING AIR SLOWLY. SO I TOOK THE CAR TO EXECUTIVE WHOLESALE TIRE. THEY FOUND A BULGE ON THE INSIDE SIDE WALL, EXACTLY THE SAME LOCATION ON THE OTHER TIRE. THE DEALER STILL INSISTED THAT I MUST...