I have updated the firmware on my Nikon D7100 to C1.04. At that moment, my Nikkor 18-200mm f/3.5-5.6G AF-S ED VR DX was on the camera, and I did not notice any problems. Today I put my Sigma 17-50mm f/2.8 EX DC OS HSM on the camera (my walk around lens) and discovered that autofocus was no longer working. When I press the auto/manual selector button while in auto mode, the control panel on top of the camera starts blinking, and the lens doesn't focus. It is possible to select the A, C, and S modes of auto focus, despite the blinking, and also to select the Area AF mode. My other lenses (Nikon 18-200 mm and Nikon Nikon 35mm f/1.8G DX AF-S. as well as Sigma 10-20mm f/4-5.6 EX DC HSM) continue to autofocus normally. Has anyone experienced a similar problem: after the firmware update, or without any firmware update? I have to decide whether to go to Nikon with the problem, or to Sigma. I would appreciate advice.