> I had a similar issue with the same model lens and my D700 >while at a NASCAR race in Michigan. My problem was only >temporary though, I flipped the switches, looked at / wiped >the contacts, and remounted the lens several times, I stopped >using it for 20 minutes or so as I went for a refreshment. >When I took it in hand again to change lenses I tried it once >more and it worked fine and has been ever since. I’m not sure >what happened.
Went to the back door and shot at three different focus points with a 35-70. 3.3-4.5 and focus was quick and accurate on the D600.
I remove that lens and put on the 28-105 and shoot at the same focus points, the middle distance the 28-105 will not find focus. I had cleaned sensor, flipped switches and such before trying it.
I put the 28-105 on my D90 and it seems to focus at all focal lengths.