Hi all,
This is a very old thread but I'm going to answer anyway, just for the record.
My D2H with nearly 20.000 clicks recently started to display "Err" too. Pushing the shutter button produces a (black) picture and 'fixes' the issue temporarily. I have noticed that the "Err" message appears only when the picture taken is the first in a long time, e.g. the first of the day.
Luckily I bought a 5year warranty with the camera. I will send it back soon... after 花見 season!