You can only have THREE maps with custom classes....that is any class set that's not in one of the three base maps.
I'm sure there are more than three of them in that pack.
Here is a list of the ones on impulse that have custom classes:
viewtopic.php?f=15&t=460I used to have every map listed....I still have the old map page somewhere and that's what Nub used to make his....could yews it for now.
Anyway...just try maps a few at a time or something and if you get an error that says something about "EOF," just exit the game and remove the last few maps one-by-one until you don't get the error.
Some nerd should have made a program that checks for that by now....and maybe some kind of map manager with it....damn...wish I were better at programming.
~archi