We had an interesting post in the Nikon AF lens Forum that is relevant to evaluating a used DSLR. Apparently wear on the contacts with the lens can result in a FEE error. Buyers of used equipment should use a macro lens and photograph the contacts for a close examination of excessive wear.
We don't have a clear answer on the cause of the wear. It appears to be related to the contacts on the lens - and any flaw in the lens contacts can damage the contacts. Larger or Heavier lenses may also be more problematic.
I would have never thought to look at the contacts - but the problem seems clearly documented.