My understanding is this could be something to do with using multiple textures for the character.
This is taken from Disturbing13's tutorial on the subject
Quote: "*Q-when i export like you said i get a character with animations and all, but it is completely black in the fpsc(textures appear in milkshape, but not fpsc). there are no textures of any kind on it. how can i correct this?
A-Are you sure you have the correct amount of textures? Usually if you have more than one texture you run into this problem. Although it is possible to use multiple textures, if you are only useing one texture for the model in FPSC it must also only have one in Milkshape3d."
and
Quote: "for the invisible problem make sure you have only one texture assigned to the model in milkshape when you export. i had a huge problem with invisible models myself. then i assigned only one texture like D13 said and the model imported into FPSC great. i hope i helped or at least gave you something new to try out."
Hope this helps. Please post if it does as I'm modelling a character at the moment and would like to know a bit more before attempting the texture part.
Thanks