Nikon D40 help?!

Your twin sister #&%@ed up your camera.

Have you ever cleaned the contacts on the lens and the camera body where they meet? If not, do so now with a cotton swab lightly dampened with rubbing alcohol.

The letters you're referencing is the M/A (manual / auto) focus switch. The lens has this switch and operates in Auto Focus mode when set to "A" and manual focus mode when set to "M".

You have to manually focus on the subject when in letter "M". If you do not, the result will be out of focus. From your description, it sounds like the camera / lens combination is attempting to focus and operate the shutter in auto, and focusing in manual; but due to some type of damage resulting from possible mishandling, exposure to dust, dirt or even moisture is interfering with the successful completion of the process.

You could isolate the problem to determine if the cause is in the lens or camera by simply attaching the lens to another compatible Nikon camera or placing a different auto-focus lens on your D40. The problem will either stay with your D40 or follow the lens when attached to a different camera. It is also *possible* that due to numerous attempts of auto-focusing with your D40 & lens combination, that both the lens *and* the camera have been damaged. If the problem is severe enough, the problem in the failed device could cause failure in the otherwise normally working device, too.

You might be best served by contacting Nikon Service & Support below:

http://www.nikonusa.com/Service-And-Support/Service-And-Repair.page

You also said you lost your manual. You can download the manual for the D40 directly from Nikon in your choice of English, French or Spanish from the link below:

http://support.nikontech.com/app/answers/detail/a_id/14157/session/L3NpZC9YRTgxQVpKag%3D%3D/kw/D40%20manual/p/19%2C334/c/187/r_id/116678/sno/0

Good luck!

What camera body? This lens doesn't have an internal focusing motor and thus will not autofocus on the D40/D40x/D60/D5000/D3000.

1 Possiable dirty lens contact terminals
2 Auto focus motor in lens is jamed/malfuntion
3 Auto focus engagement pin on camera body is not engaging the lens
4 Correct lens,old nikon lens and some 3rd party lens wont work on the D40

THERE is a problem in lens not with the UV filter
remove the lens clean the contact of lens & camera if not working repair or replace it

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.

The G series lenses won't work in AF mode on the newer, entry-level Nikons. They require the DX series.

Camera wont let you take a picture until focus is locked, why are you using M (manual focus) if you expect autofocus to do it for you? In M mode it is up to you to focus correctly or camera will not take the picture.

When the camera is in auto focus mode, it will not take the picture until it locks onto a subject. If there is not enough light, the camera will "hunt" for something to focus on. Since it can't define any edges, it won't allow the shutter to release.

The D40 base model does NOT have a powered focus lever for autofocus, so if the autofocus is not working, suspect the lens.