Nikon D80 error shows "--" in the top screen

My lens is on tight and I'm getting this error.  I have swapped out battery 2 times and no luck.  I would appreciate any help you can offer. 

What lens, and is the lens locked at minimum aperture? 

It would be helpful like eff asked to know some more details about the camera / lens but I scraped this up. It looks like the contacts on the camera side and the lens seem to get dirty, found a guide .

So you got yourself a brand new DSLR and after using it for a little while got the dreaded “Err” error on your camera LCD? Fear not, your camera might not damaged and there might be no need to return it back to Nikon, as they suggest in most camera manuals.
The reason why this error comes up, is because your camera is not properly communicating with your lens due to some dirt and grease both on camera and lens contacts. The solution is pretty simple – all you have to do is dismount your lens and clean the lens contacts, then clean camera contacts and mount the lens back on the camera and see what happens. Sounds too complicated? Are you afraid to damage your camera and/or lens? Then keep reading, because I will show you exactly what needs to be done.

So here is the step-by-step process:

1. Dismount camera lens – before you remove the lens, make sure that you are doing this in a clean environment indoors. I prefer to do it at night (when kids are sleeping) in the bathroom If you have not dismounted a lens from your camera yet, now is the time to learn. Turn off your camera. Press the lens release button located to the left of the lens when the camera is viewed from the top, then rotate the lens clock-wise to dismount the lens as shown  here . Right after the lens is dismounted, put the black plastic camera cap back on the camera lens mount to prevent dust from getting into the camera.
2. Clean lens contacts – there are many different cleaning solutions out there, but I would recommend the following approach: first, wash your hands with soap and dry them out. Next, put some denatured alcohol (ethanol) on dry, light-colored microfiber cloth, wrap it around your index finger and gently wipe each lens contact in circular motion without touching the glass on the back of the lens. Here is how the contacts look like on the Nikon 50mm f/1.4G lens:

   

   
   If you can see dirt or grease on the microfiber cloth, repeat the above process again using the cleaner part of the cloth. Once you are done cleaning the contacts, use the  Giottos Rocket Blower  to blow away any particles your microfiber cloth could have left on the lens.
3. Clean camera contacts – remove the black cap from the camera lens mount, then use the clean portion of the same microfiber cloth and gently wipe the camera contacts, just like you did with the lens contacts. Here is how the contacts on the camera look like:

   

   
   Hold your index finger with your nails facing down and while holding the microfiber cloth, move from left to right and vice-versa several times. Repeat the process one more time with the cleaner part of the cloth to make sure that there is no dirt/grease left on the camera contacts. Make sure to do this rather quickly to prevent dust from entering the camera chamber.
4. Mount lens back on the camera – once all contacts are clean, align the dot on the camera with the dot on the lens and fully mount the lens in counter-clockwise direction.
5. Test and make sure that the “Err” message is gone – now turn the camera on and take a few pictures. The “Err” message on the camera should be gone!

What if you are still getting the “Err” message? Try another lens and see what happens. If nothing changes, your camera could be damaged, so call Nikon for support.