In an effort to reduce our gasoline consumption my wife decided to ride to a meeting that she had this last weekend. It was about 5 miles away. The bike had been put away for a while due to her pregnancy and childbirth. It sat on the trainer for about 6 months and got occasional use. I topped off both front and back tires and checked air pressure at around 50 pounds (for road use). She got to her destination without any problems. Turning around to come home after her meeting the tire went flat after about 1 mile. Being the well trained (by me) female that she is, she changed the tube in about 10 minutes and got back underway. She made it about 3 1/2 more miles before the second tube expired in the same fashion as the first (more on that in a moment). Being that she was carrying only a single spare tube, she was forced to walk her bike the remaining 1/2 mile home. Examining the tubes later, we were unable to find any sign of holes or puncture marks. I guess that's good since She using the Specialized Armadillos, which are nearly impervious to puncture. We eventually found that both tubes had gone flat because the stem (Presta) had been forcefully removed from the rubber of the tube. The first one was torn about 1/2 way around the base of the stem while the other one was completely torn free from the rubber. I was planning on going down to purchase 2 fresh replacement tubes but I wanted to find out if this is going to be a recurring problem first. Since it already happened twice, it could happen a 3rd, 4th, and 5th times as well. What caused this strange tube destruction and how can I prevent it in the future so my dear wife doesn't get stranded? I'm sorry if the post seemed overly long. I wanted to include some information that I thought might allow true technicians to discover the problem.