I have had a number of "events" in which the camera tells me that it can't identify the installed lens (the 16-50) and the lens extension does not retract when the camera is turned off. The first time this happened to me I recalled a tip I read years ago for another camera brand (pulling the battery). I tried it and it fixed the situation. But yesterday this happened to me 2 or 3 times and battery-pulling didn't help the condition. Once it was just time that fixed it, another I had to switch lenses (then when I put the 16-50 back on it worked). I should probably add that this camera is less than a month old (so dirty contacts are not likely) and I could obviously return it for a replacement, but it works fine (so far - keeping fingers crossed) with the 20/2.8, 16/2.8 and 50/1.8. Has anyone else here had this issue? And if you did, what did you to to prevent it?