I had this problem in Low light with the AF Assist Light still coming on.

What I found was that using the Live View is completely different to focusing while keeping Live view off. 

I just stopped using Live view and the problem was immediately solved. Of course the AF Assiste light was working in my case for both scenarios.

Nikon D3100 Won't Take Photo -- says light is too low
How do I display zero value as blank cell in mac numbers 3.1 yet maintain a formula.  I want a running balance column that only shows balance to the line of the last entry like a checkbook register.
Thanks.
