Why won't my Nikon D40 take pictures?
I have a Nikon D40 which is less than a year old. It will take pictures on the "no flash" mode, the portrait mode and the sport shot mode, but not any others. When I use "auto" mode, the flash pops up, it will focus but the shutter will not click. I have charged the battery and changed the SD card, restored the factory settings, i just can't figure it out. I love this camera, I just want it to work again!
Sadly, the only thing now would be to send it to nikon for diagnosis. It could be that some contacts wore out over time or a wire came loose, or even a firmware issue. Call nikon at 1-800-Nikon-US (assuming you are in the US) and ask them about it
I have a D40X, and it's pretty finicky about focus and lighting compared to other cameras I use regularly.
My guess is that you simply don't have enough light in the scene. This would be the case if you turn your lens' A/M autofocus switch to M for manual, and it does take a (blurry) picture.
The AF system may also get confused if there isn't a strong edge or pattern in its target areas (the three bracketed regions in the viewfinder).
Nikon Speedlights (flash heads) have their own AF system. If you can borrow or rent one, try shooting with it on to see if it helps. The SB-700 starts around $330, though you can likely find other units used for cheap.
Use the "P" (Program) shooting mode if you don't need a particular "easy mode".
You have a lot of possible issues going on.
In the "auto" mode, the flash is supposed to automatically pop up.
Why are you still using P&S techniques with a fully adjustable dSLR? If you just use the camera as you would any fully adjustable camera, 35 mm or dSLR, much of your frustration will just go away.
Have you ever attended a class in photography? Do you understand the fundamentals of photography and know how to use your cameras light meter.
You do know, don't you, that in very low light auto-focus will not work and most Nikon cameras will not allow you to take an out of focus photo.
Start over shooting in bright sun, using the camera in the manual mode and use the light meter to determine your exposure settings. Working from there you will see that you will have to use larger lens apertures, slower shutter speeds and higher ISO setting as you move indoors and begin shooting in lower lighting. Until you get full control over your camera using manual settings, avoid using any of the so called modes that can be used as "training wheels", but really don't allow you to learn how to use your fine camera