I've been getting this error for about a month with my d5100, which I've owned for about 14 months. Rico's advice didn't do the trick for me. Here's the weird thing: if I put my old 50mm f1.8 ai lens on the d5100, the camera works fine. I can take as many pictures as I like without any error messages, shutter problems, etc. Of course, with that lens I don't get metering or autofocus. As soon as I put on any kind of AF lens (I have both AF and AF-S) I get the error message. I've switched SD cards, made sure the battery is fully charged, taken the battery out of the camera for an extended period and put it back in, reset the camera, and I still get the error.
So, I'm pretty sure the problem is electronic rather than mechanical, and that the camera needs to go in for service. My question is: is it worth it? The camera is no longer under warranty (I bought it used), and I'm in Rome, so the repair would be done in Italy. Does anyone have any idea how much repair might cost here? I will be returning to the US in a few months if it would be significantly cheaper there.
Thanks for any advice!