And, you might accidentally slide the switch on the lens to manual. I do that now that I am using a sling strap...in fact, it's happened more than I'd like. The first thing that I checked was the CSM leaver on the body...but it turns out that with the camera swinging on your hip, that the lens slides along your belt loops will move the lens switch to manual...and give you the same problem. Suddenly, no autofocus...
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