Some of the later Neo Geo CD games used copy protection. The front and top loaders didn't use it... but the CDZ did! Some of the later games have been patched to work on the CDZ. I don't know if you're using images of games to build these, if you use a later game it might be the cause?!?
I'll see if I can get my toploader to work (broken lid) to double check.
Thanks for all the effort..especially for Shinobi..!
Eswat and Alien Syndrome next...?