Why won't the self timer on my Nikon D3000 work?

I had the camera for about a month and it was working fine until I turned it on last week. I tried pressing the "FN" button to set it on self timer and the screen just turns black until I let go of the button. It hasn't done that before. The only way it works is if I set the command dial to GUIDE then set it to self timer then it would work. But I want to use it with other commands. What's going on?

You really, really need to spend a lot more time with your camera in one hand and the user manual in the other.

Look on page 134 again. You have to press the Fn button and then press the self-timer button. Just pressing the Fn button only changes your options on certain buttons and menu settings