My recall reflects Brian's. The discussion evades my search skills. I think the firmware is designed for taking class photos. Each child is given a barcode which is scanned when you take their photos. The photo name ties back to the barcode and the barcode back to name, class, grade, school, etc.
I don't recall how to revert it. You could send it to Nikon and ask. The worst that'll happen is they send it back without repair.
Does the firmware flash a manufacturer's name or give clues? I found www.halseimaging.com via Google but it is blocked on the USAF network in Kuwait (for my protection, I'm sure). It popped on a search for: d2x class photos automation barcode