And I'm pretty sure it's my fault
I recently acquired a used 70-200 VR1 and today was the first day I tried to use it in AutoFocus mode - I shoot 99% Landscapes and 99% of the time in Manual Focus mode
I made the obvious adjustments
switched the camera from M to S
switched the lens from M to A
But the AF did not respond
To make sure it wasn't a problem with the lens I came home and tried the 70-200 on my D700 and the AF worked fine
So, I must have made some menu change on my D3S that is causing the AF not to work
I would appreciate any suggestions as to what that might be as I would prefer not to return my D3S to all the original settings
On other lenses does the AF respond on the D3S? In the menu double check that half pressing the shutter down is set to auto focus (if you like it that way, if not double check the AF button is set to auto focus)
Maybe you have the AF set to activate only with the AF-ON button, and not the half-press of the shutter button. You can test this by attempting to AF with the AF-ON button.
I had the same thought as Rodolpho - my 80-200 f/2.8 was driving me crazy the other day until I realized I'd set up the camera to AF only with AF ON. Oops!
Rodolfo Paiz wrote:
Maybe you have the AF set to activate only with the AF-ON button, and not the half-press of the shutter button. You can test this by attempting to AF with the AF-ON button.
I love happy endings , even if they make me look foolish
I prefer to lock focus when I depress the shutter release button and I had fiddled around with the AF-ON button and forgot that I had set the "Shutter release button AE-L" to Off in the menu
Switched it to ON and and the 70-200 is AF'ing like a champ on my D3S
You guys shoot funny 
Glad that was it, Bob 