Tire Bubble problems of the 2007 Chevrolet Silverado 2500

We purchased a set of bf goodrich tires on 5-16-2009. The 1st incident occurred 7-11, driving home noticed a bad thumping sensation in the right rear tire. Pulled over and noticed the tire had a bubble in the center of the tread, so pulled over and changed tire. So on 7-29-11 I purchased 2 new tires to replace this bad one. The 2nd incident took place on 5-11-12 was a blow out and no warning. So I changed this tire as well. On the same day I felt a thumping sensation so pulled over and noticed the left rear tires had a bubble. So of the 4 tires purchased 3 of them went bad. I pulled the other tire of my truck and purchased 2 new tires on 5-12-12. I submitted a complaint to bf goodrich to see if they would either cover the cost of the new tires or the damage to my truck. Needless to say the claim was denied. I provided them with all of the maintenance paperwork showing the tires were rotated on a regular basis and the pressure was checked on a regular basis. Their answer was the tires were run on a 'runflat" condition. That the tires were run on in a flat condition. Now how could anyone possibly drive down the freeway with no air in their tires. And how would 3 tires so far go bad.