Thanks for the help guys. Here's my code...

c_move(me,vector(4*(key_cuu-key_cud),4*(key_cul-key_cur),0),vector(0,0,-1),GLIDE || IGNORE_MODELS || USE_BOX);

I fixed the problem. That's quite interesting USE_BOX isn't the same since the last update, because now that I think of it, that's when I really started having the problem.