Stuck shutter D100 Nikon

I have a 5 year old D100. I had the shutter box replaced about 18 months ago by Nikon. I worked OK for a while. Now, the shutter locks up until I push the shutter release again. Then it clunks and the mirror comes back down. There is that dreaded error message and then a few clicks later, it clears up. Now, I took three pictures and the shutter locked up and all I get when I press the release is a whirring sound, like an auto-winder on a film camera. No shutter activation, just continuous "err" message and an "R06" where the frames remaining counter is. It seems totally locked up. I took off the lens, remounted it, cleaned the contacts, took out and replaced the battery, took out the CF card, replaced it, hit the camera a few times with my palm...nothing but that whirring sound on shutter release. Any ideas?