a few things come to mind...

-Do you use c_move only for moving (forward,back,left,right), or do you also use c_move for the gravity?
-Do you use glide?
-How have you set max_x and min_x? Do you also use max/min_y and max/min_z?
-Have you tried using c_setminmax(me); instead of manually setting the collision hull size?
-If you character can also rotates... Do you just change the angles directly, or do you use c_rotate?

Not much more people can do for you though, if you don't post your movement code...