How to fix my Nikon D90?

I have a Nikon D90 with sigma DC 18-200 mm lens. Anyway, I put my camera away for a while and I brought it back out. Everything was operating fine… I took a few pictures and transferred them to my PC… After that I found that my playback button and my live view button don't work… Nothing shows up on the screen… I know the screen isn't broken because I can access the menu but I can't look at my photos or anything. I also noticed that my camera doesn't show me a preview of photos right after I take them… How do I fix this…

Added (1). Yeah, so I know almost without a doubt, it isn't a problem with my menu settings… My LCD screen just won't show ANYTHING except for when I push the menu button and the info button…

The D90 has an LCD Brightness control. It's on page 202 of your manual and you can find it in the Camera Setup of your Setup Menu. Check to see if it isn't turned all the way down.

As for the the Image Review, what you call preview, it can be turned on or off as per page 163 of your manual.

If the LCD Brightness is at 0 or higher and the image review is turned on and you still don't get photos on your screen, contact Nikon Service and Support and expect to send in your D90 for repair.
http://www.nikonusa.com/...pport.page

There are two kinds of resets you can do on a D90, one reset will reset everything but your custom settings, and the other is a factory reset that does everything.

Try both resets to rule out any errant setting you may have done, or any goofy mode the camera may have found itself in.

On the D80 if you push the playback button you can scroll thru settings by using the multi selector or main command dial. Pushing the selectors different arrows causes different settings to show in the screen as well as using the rear command dial. Off is one selection. Try holding the playback button and start pressing or rotating the above buttons, maybe you'll get back to a functional setting.