Nikon D3000 problem with taking pictures?

I bought this Nikon 2-3 weeks ago and was working like a charm! Today a friend came and wanted to see the camera and i took some pictures to see the quality. In the 3rd picture it was black. I said thats odd. I took another picture and was black too! I suspected something on the settings or something but it was ok within those minutes, i was taking pictures and suddenly blackness! I reset the settings and still the same. I removed and replaced the battery and the lens i changed memory card and still black! It couldnt be more black than this!
Does anyone know what's going on here?
Please help! Thank you.

Added (1). Fhotoace with respect on your experience, i said that i was taking pictures and the 3rd picture taken it was black! With out changing any setting! I even reset the settings! I took a picture of the sun too and its still black! Not a single white frame in it. The settings are exactly as it was the first time i used the camera

Added (2). Jim A, thank you Jim i really appreciate your effort! Where can i send the good & bad pictures so you can get it?

You need to sit down with your camera in one hand and the user manual in the other and learn how to use the controls on your camera

A dark or black image is the result of gross underexposure, not any problem with the camera, memory card or batteries

Take a look through the view finder and see what the light meter is saying. My guess is that it is pegged into the - 2 range

Call Nikon and they will help you take control of your camera. 800. NIKON-UX

Here is the link to Nikon support http://support.nikonusa.com/...l/a_id/238

and the correct number for the US Is 1-800-Nikon-US (1-800-645-6687)

Since this seems to have occurred suddenly and out of nowhere I'd get in touch with Nikon and tell them the situation. Make sure however that you include a shot that is good and a shot that is bad.
I'd also make sure that the settings on these shots are the same. They will be able to read the exif
data of the shots. If the settings are correct for the particular shot they'll be able to tell a lot more about what may have happened to the camera.

Perhaps your friend twirled a control without knowing it. Try the following.

1. Make sure the selector dial on the top of the camera is set to A (auto) or P (program) mode. I'm guessing that you have it set to M (manual) mode.

2. If the above doesn't fix it, try resetting the camera. See page 119 and 125 in your manual.

3. If the above doesn't fix your problem, take it to the dealer you bought it from and see if they can get it to work or give Nikon a call. They may be able to talk you through the issue or you may have a broken camera.