Tire Valve problems of the 2003 GMC Envoy

On 6/3/2008, I purchased 2 michelin ltx m/s 245/65/17 tires for my 2003 GMC Envoy from, millennium autobody & service inc. , 1782 main st. , brockton, MA 02304. On 10/22/2008 (after only 7969 miles) the tire blew out on the way to FL- had it been replaced in NY. The tire was shredded. On 11/10/2008 (after only 9557 miles ) the 2nd tire went flat- I was able to pull the SUV over quickly recognizing the same sounds and vibrations from 1st blow out. This tire was not shredded. There was no punctures/ cuts to the tire. The clerk at the tire kingdom in FL stated that it was a faulty tire valve stem that had caused the tire to fail. I called home, and my family advised me that there had been reports of bad valve stems on trucks and SUV's. I contacted the location where I purchased the tires to report the two tires failing- they requested that I bring the tires back when I came back to MA. I did not have the 1st tire- but I did get and still have the 2nd tire. Millennium autobody said they were going to talk to tire rep and get back to me- but it has been several weeks now and still no word. I was very fortunate that no one was injured during these 2 events- I fear that there are still faulty tire valves out there- that other consumers may not be aware of them.