Good, I'm glad to know I'm not the only one. A little history, the front tire is new with just over 4000k on it, the rear 200 is fairly new, I got it the last time we went to yanks. I guess about 1 month ago. Odd thing is both stock dunnys did it, and the new one is doing the same thing. I've taken them off and dunked them and I get no bubbles. I really think its the valve stem.I hate to goop it because that stuff eats the paint.
Go to the auto parts store and get a valve core wrench (or a Schraeder valve tool -- same thing). It's cheap and you can tighten the core in the valve stem; that could be the problem. They pull the core to seat the tire and don't always screw them back in tight.