There are two focusing mechanisms - screwdriver and electronic (AFS). Do they both fail to AF? Is it possibly the trigger mechanism, ie does AF-ON work? Finally, take a look at the contacts in the lens mount - there might be something interesting there.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!
OMG! I think you may have hit the nail on the head (I'll check when I get home from work). I usually only use this camera now when I'm birding (to get the extra reach), and that's the one time I use the AF-ON button. It's one setting I didn't think to check when this happened on the weekend.
I am curious... Why do you switch between AF-ON, and using your shutter release for focusing? Once I started using AF-ON, I never went back to a shutter focus - it was too confusing. AF-ON becomes 2nd nature after a short period of time using it. The only problem I have had with it is when I lend my camera to someone so they can take a shot with it.
A side note: I have introduced several photographers to AF-ON, and they have *ALL* gone to exclusive use of it.
I can't speak for Doug, but in my case I find when I'm shooting sports that managing both buttons for thousands of shots is a bit fatiguing for my hand. Also, I'm frequently rotating between portrait and landscape orientation, and the AF-ON button on my D3 is not in the same position relative to the shutter button in the two orientations, which is annoying. Since decoupling the AF from the shutter doesn't provide any real advantage for the way I shoot such events, I don't do it.
When shooting other things, I'll switch to decoupled AF if I'm shooting a mix of moving subjects and static subjects that I might want to reframe after focusing. Otherwise, I'll choose AF-C or AF-S as needed and just use the shutter button for AF.