Turns out we did have some progressive JPEGS that we had to resave as Basline Standard JPEGs in Photoshop. Doesn't explain why Kalek could load the map in base JA and I couldn't, but at least this info is here for anyone else who runs into this issue. Also, NetRadiant-custom was very helpful as it was the only software that told the user, upon loading a .map file, that there were progressive JPEGs and specifically what files.
So I managed to get it working... dunno how, I used the same method as always but now it's working. Thanks for all your help. I did want to ask if anyone could explain another small issue... the music in the JAMP menu - even using the base music - always starts from the beginning again if I go to another menu and then go back to the main menu. For example, I load up the game and the music starts playing at the main menu. I click "Play" and then click "Back" to take me back to the main menu and the music starts again from the beginning. Any way to fix this? This may be a better questions for @@eezstreet...
