lab-one, great post, but I think that people may think they need to do something other that download the proper mpeg2decdg.dll (see the stickies for link) and enable "Add to avs file" in the RB setup with the proper path to where you put it. No registry entries can then influence it. Did you have that checked? (Just to verify)
What does come to mind is what would happen to those that do
not have "Add to avs file" checked and have both mpeg2dec.dll and mpeg2decdg.dll in their plugin directory? No offense, but that it kinda nuts
I would think each one is activated by the "mpeg2source" statement in the AVS. Frankly, I don't really understand how it would even work. Maybe Wilbert might know.
Personally, I wonder if much of these problems would go away if DVD-RB would insist the exactly named mpeg2decDG.dll be in a sub directory of dvd-rb and do a crc check like Joergen suggested. It just would not work without the right version - period.