Denon DVD-3800
There are two downloads here, to the best of my knowledge, the first is a fix for the Chroma bug, the second is a multi-region update for the A1 and 3800.NOTE: I have not tested this as I don't actually own a Denon player. If this stops your player working, or turns it into a small frog, don't blame me.
This is provided with no warranties as to it's suitability, use at your own risk, always ask a responsible adult to supervise you, may contain nuts.
The downloads are both provided as a .zip file. Download them, open the file, and read the text file contained within.