I think the problem was with the center of the triangle I drawn before. After correcting the vertices, the code works ok. Next time, just as you suggested, I must "center" my objects at (0,0,0) and then move them around using appropiate matrix translations.

Anyway, I think you guys helped me work it out. Thank you very much, I'd not guess the vertices were the case of my problems.

EDIT
Nevertheless, getting it all done is tricky. After I'm done with a basic mouse-looking example, I'll post the code on the board.