Well, if you cant open levels, that means that JJ2 (MAC) has too many in the homecooked. So you need to delete ALOT. So in order to host levels in the home cooked files, you have to delete files which either you hate and will never host, so, no matter what the maximum holding capasity is, you have to delete enough files for (your file number limit) to go down from the highest number. Best do alot so it can acumulate and do the process again.
Rinse. Lather. Repeat.