Nikon d3000 not focusing?

I have a Nikon d3000 and all of a sudden, it's not focusing. Everything is blurry. I've tried fiddling with the settings but nothing is changing. Any idea what's wrong with it and how I can fix it?
Any help is greatly appreciated.

Do you have a sample shot? Is the switch on the side of the lens that you can set at A or M set to A (for "A"utofocus, as opposed to "M"anual focus)? Might the camera be internally set to manual focus (i don't think the D3000 can do this though)?

Shooting in low light? Cameras can't focus without light. Also, as recommended above, look at the lens switch for auto focus or manual.

Barring all of that pull the lens and gently clean the contacts on both body and lens - no liquids, just a micro fiber cloth.

If none of that works there's something else and perhaps you need to call Nikon.