most of the characters I've downloaded work fine, but some make the game quit when I try to use them. I can't see any difference in the files. What could be wrong?
If you are playing :ffvstr: more than likely they'll need to be converted, as most of the meshes were exported for the first game. Some work fine without conversion, others not so much.
You can get the converter here: http://www.alexff.com/eznif.php