On Christmas day I was wandering around taking a few shots, and the temperature was around -1. Not excessively cold but a bit nippy. I'd taken about 30 or 40 photos when suddenly the autofocus stopped working (Nikon D40x with 18-55 kit lens). I could hear rapid clicks from the lens but the focus ring would not move - almost as if the gears driving the focus ring were slipping. The problem seemed to cure itself when I switched from Auto focus to Manual and then back again. At this point I needed to get back for dinner so I thought no more about it When I got back to where I was staying I immediately tested the camera, and I had exactly the same problem. This time switching the focus mode made no difference, but after about a minute It started working again. Since then then camera hasn't been in the cold and it's worked flawlessly. I can only assume that warming the camera up made the difference. I'm not overly concerned as I'm just about to pick up a D90 with an 18-200 lens (or D300 but cost and personal ability is a consideration here) and the 18-55 is not exactly an expensive lens, but the question is, is this this to be expected in cold temperatures?