nikon d40 autofocus problem
this morning in fact put on 18-105 lens.didnt work,you can hear the motor,but no autofocus, left it a few seconds,tried again and it worked
You could try to clean the contacts in the lensfitting on the body.
However probably you have to take it to your dealer for a checkup.
Get a good action camera at http://actionshotcam.com