'Err' & 'E"

If there was a film in the camera and you opened the back, all the pictures you took got burned. You need to rewind the film take it out, put a new one in and try to turn on the camera. err should be gone.

Is the ERR blinking, and is there an additional blinking E on the display? If so, the film is not loaded properly.
The film is supposed to advance all the way to the take-up spool upon loading. The camera then "rewinds" one frame at a time as you take pictures. This way the camera knows exactly how many shots are left on the roll. Also, if the back is accidentally opened, the shots already taken are already in the can and won't be ruined.
If you need a manual, you may download a copy here.
Try cleaning the battery contacts and see whether the battery reads full with no film in the camera.
If problems persists, feel free to reply to this post and give any additional details.

The manual mentions only 2 conditions where the Err message appears. First if it is Err + E at the same time, the film has not completely wound and needs to be reloaded.

If it is Err alone, the manual states to fire the shutter and see if the message remains. If it does, to contact a Nikon Authorized Service Rep.

The Err message alone indicates that a malfunction has been detected, and the manual recommends to fire the shutter and check for the message to clear. If it does not, to contact a Nikon Service Rep.

If it is Err + E, the film did not advance properly and needs to be reloaded.

Jim, it really sounds like one of threethings. Either will require a repair shop.
1. the film sensor is not recognizing film in the film chamber, or film across the back, therefore not telling the advance motor to advance film...
2. The film advance motor itself needs replaced.
3. The rear door latch switch needs replaced.
Since everything else seems to do OK, I doubt the main computer board is bad.

It could be that your camera doesn't know it's rewound the film already. With the camera turned on, push and hold BOTH manual rewind buttons simultaneously - one near the release button ( +/- ) and the other toward the front of the camera at the lens release button. Try the release button again.

There are several situations when this message happens and the camera locks up, and almost none of them has anything to do with the cause stated in the camera manual: film DX coding error. (If it is truly a DX-coding error, manually setting the ISO speed of the film should solve the problem. This could happen in cold weather.) Scenario One: when using Alkaline batteries and the batteries are almost exhausted, and yet one continues to shoot. The battery may not have enough power to complete the shutter firing operation (which usually includes: mirror up, close down diaphragm, shutter fire, mirror down, open diaphragm, advance film, and charge the shutter for next frame). The camera could be lock up in the middle of the operation, left with a dimmed viewfinder. Usually an indication appears quite early if one pays attention: when the batteries are almost exhausted, the film advance becomes noticeably slow. In normal situation film advance is very fast and one cannot distinguish it from other noise such as mirror flipping. When the batteries almost exhausted, the film-advance could take almost 1 second, and the noise of film advancing has been mistakenly identified by some as "beep". I think those is the result of over-adjustment for the Premature Battery Indication problem. This scenario is particular to using alkaline batteries, due to the peculiar behavior of the alkaline battery: even when its power is almost exhausted, it still has a pretty high voltage. Solution: replace the batteries and fire the shutter once should solve the problem. I am pretty sure this is normal, since it happened to me several times, and I once deliberately repeated this happening. Scenario Two: At the end of a roll, when the remaining film is too short for one more frame but long enough to fool the camera, the camera could end up with "Err" message. Solution: rewind the film and load with the new one, and possibly fire the shutter once could solve the problem. (This has never happened to me, but summarized from other’s reports.) Scenario Three: I've heard of two reports: happened in the middle of a roll, with sufficient battery power. I have no idea what’s going on. (Could be really a DX-coding problem, which does not necessarily occur just at the beginning of a roll.) Solution: probably should send the camera in for a check. (Also, both reports of this problem occurs while using Kodachrome films.)

Make sure the lens you are using on the camera is set to the minimum aperture setting. i.e. f22,f32 (highest f stop number)

You may have to manually rewind the film that you just loaded and try again. The is a manual rewind button on this camera. Before you load the new roll, check the condition of the shutter curtains/blades. Do they look out of place or pushed in?

Needs new batteries, or the film isn't loaded properly. Check the battery area for rust too and clean the contacts gently with a pencil eraser.