Nikon D3000 auto focus won't work?

I got a Nikon D3000 one month ago and I'm still using the 18-55mm lens. I never had any problems at all until yesterday when I tried to take a picture and it would not focus. I tried everything and it does not work. The only way I can take pictures now is by pressing the AF-L button when it's focused…
I tried to reset to factory defaults, but I noticed that I do not have a reset button? I read on the user's manual where it is supposed to be, but instead of a button, I find a tiny hole there…

Can somebody please help?

Rather than resetting, which could be done by sticking a pin into the hole btw…
use your user manual to find your focus settings. You probably changed it to MF, whereas you would like to have it in AF-A.

I can think of 3 things:
1. Auto focus switch on lens isn't set to auto. However, if this was set to manual, it would let you take a picture without requiring any other button pushes. Page 16 in your manual.

2. Focus mode set to manual. Again, it would let you snap a shot without reqiring any other button pushes. Default setting is usually AF-A. Page 42 in your manual.

3. Your lens contacts might be dirty. Rotating the base of the lens (like you're trying to remove it) gently back and forth a few times usually will clean the contacts sufficiently for the auto focus system to start functioning again. This seems to be a problem with Nikon's kit lenses. I would venture to guess that this is your problem.