My Nikon D80 sometimes got stuck and won't focus or take pictures at all. I didn't find any 'solution' except for wait for sometime and hope it will 'recover' itself. Anyone has an idea what's going on?

I would try to determine if the problem is in the camera or the lens.

Make sure that the battery is still able to be charged to a level that will operate the camera. If this is the original battery and / or has been used extensively, it may be time to invest in a new rechargeable battery before continuing troubleshooting.

Make sure there is a memory card in the slot. If it is full, clear some room on it.

Perform a "Two Button Reset" on the camera outlined on page 44 of the manual to restore the D80 to factory default. The two button reset is done by pressing the (+/-) key and the (A/F) key (both on top of the camera) at the same time.

Some Nikon lenses are not compatible with every Nikon camera, so that may be a place to start if you're not using a kit lens (you bought the camera and lens together as a kit - not the camera alone as a "body only" sale). Review your manual for a list of lenses that will / will not work with the D80.

Assuming you're using a compatible lens, try swapping the lens to another compatible lens. If you do not have such a lens, bring the camera (preferably w/o the lens you own) to a store that sells lenses for your camera and install the lens on the D80 body. See if the camera functions. If it does, you know that the other lens is most likely the cause of the problem and you'll have to decide whether to repair or replace.

If unable to get to a store that sells lenses, an excellent lens for the D80 is the Nikon 50mm f1.8 prime lens. It gets great reviews and at about $100 is significantly less than 1/2 the cost of the only slightly faster 50mm f1.4 prime lens.

Make sure that the contacts on the mating surfaces of both the camera and the lens are clean. Dirt and dust can interrupt signals sent between the camera and lens.

If still nothing works, you could contact Nikon Support for a solution below:

http://imaging.nikon.com/products/imaging/support/index.htm

I hope this helped!

It happen if the lens in not connected very well on the body, even if you here the click, it wont say it makes good contact. Try to detach and install the lens again.