This weekend, the four rightmost points for autofocus have stopped working in Single point mode on my D5100 (just over 1yr old). If I try to use them, the lens moves out of focus (I'm guessing all the way in) and then stops trying to focus, but if I then switch to any of the other 7 points, it will work fine. It happens with all of my lenses (Nikkor 50mm, 55-300mm and the kit lens). I think that the problem is limited to just those four points, though toward the end of my trip I thought it might have happened once or twice on the left side as well (possibly getting worse?)
Any suggestions for what to try before sending it off would be great, especially with the holidays coming up!