I have a nikon d-40 is there a seeting on it that well let the cameras lens focus when you push the button half way down. I took picture but I had to manual focus I don't know if it the lens or this camera is only manual

do you have it set on automatic focus and if so you may have a bad lens
push shutter buton half way down when select in auto it will focus it for you if that don't work send lens in

When the lens moves in an out it is TRYING to focus. In some conditions the auto focus gets confused. Move your field of few and press the shutter button down half way to lock in focus. Then move it back (to original view) and finish taking the photo (pressing down the rest of the way).

The r11 is in the lower right of the top LCD or view finder that is in the D80 manual page 36 it speaks about the buffer. The r with a number is how many shots the buffer at that moment can handle. It is not an error message. For auto focus issue is the lens in AF as well as the camera?

your camera works fine, but they made it like this, so you should push the button all the way down, not half way, because when you push half way, the camera focus on the target, and the little lasers flash, but that is no shoot... on the other hand, if you push half way the button, the camera focus on the target, then you push it more, then you shoot the picture and it is saved. Try to be more careful about what means all way down and half way down.
Hope it was helpful

has the lens stuck up? put it temporarily on 'M" and try to turn the focus ring. this should be freely turning;

otherwise you may want to check the camera body to lens electrical contacts (silver).. a small dab of alcohol to a q-tip.. make sure its not that wet..then try to clean the contacts.

you push the button half way down (sounds crazy) but that is when you are letting the camera know you want it to focus and when it turns green push the button the rest of the way down

You can adjust the number of focus areas so that it will not try to compensate for many objects in the pic at 1 time

Look on the left side of the lens. Make sure the button is on A for auto focus and not M for manual. OR not stuck in the middle. Hopefully that will solve the problem.

This happened to me once on a D70... When mounting the lens, make sure it clicks in all the way when turning counterclockwise. Also it may be worthy to note that both the lens AND the camera must be set to autofocus mode ("A" switch set on both lens and cam).

Marky

check for dust specks on the lens glass.