I was having intermittent trouble with my new D90 recently. The dreaded blinking “ERR” in the LCD. My symptoms included: wouldn’t focus, shutter would trip but no image recorded, ERR light. The only way to clear it was to remove the battery. The thing is that it would only happen once in a while so, at first, I didn’t think too much about it. It got bad enough though that I decided I had a bad copy and was about to send it back for a replacement when… I noticed that the LCD would flickr when I wiggled the lens.
The solution? I removed the lens, wiped down the contacts and the mounting ring, and reattached it. Problem solved. I feel a little sheepish admitting how lame/lazy I am for not checking that in the first place. Lessons learned? I’m an idiot. Plus, check the lens mount if you’re getting weird intermittent mechanical problems with your DSLR.
Click on the following link for a review of the Nikon D90 camera.