Hey man, thanks a million. There was a file with ".dds" as part of the name of the livery file. I never noticed it as I was expecting to see .dds files, it was only when you said to re-check that I realised one of my custom liveries was off.
The tool works perfectly, the problem was my own stupid re-naming files. I just got a free copy of Photoshop & was messing around editing liveries for the first time & doing such things for the 1st time while a little bit drunk probably isn't the wisest of moves.