Nikon D40 won't auto focus?

Standard AF-S 18-55 lens.
Lens switch set to A; in auto mode. Half press the shutter release and it does focus (motor whirrs, lens moves etc.) but the in-focus light is flashing and the shutter won't release.

Have tried AF-Lock - no change.

Any Clues?

Try manual exposure mode. If camera exposure ( on top lcd, if it has one ) reads HI or LO, it will not fire.

Call Nikon and ask them.

800.NIKON-UX

Hopefully you did not buy a used one from an eBay seller and got one that does not work

The problem you described happens when the subject is too close.
Try to use full manual and see if the shutter will be released.

If the camera doesn't beep, it won't let you fire the shutter. Therefore if there's not enough light or if the subject is too near you will be unable to get a focus lock and therefore you won't be able to fire the shutter.