Problems with CharacterController.Move

Hi,

I am trying to make a Main Character for a 2D platformer. I'm using a CharacterController. The problem is, when I try to use (a modified version of)the script from the CharacterController.Move example, it doesn't quite work. I can move left (velocityX < 0) but it won't move right. Even when velocityX is positive, my cube won't move right!!!

I'm totally confused, any suggestions?

 var speed : float;
 var jumpForce : float;
 
 var velocityX : float;
 var velocityY : float;
 
 private var controller : CharacterController;
 private var gravity : float;
 
 function Start () 
 {
     gravity = -Physics.gravity.y;
     controller = GetComponent(CharacterController);
 }
 
 function Update () 
 {
     if(controller.isGrounded)
     {
         if(Input.GetAxis("Horizontal") > 0)
         {
             velocityX += speed;
         }
         
         if(Input.GetAxis("Horizontal") < 0)
         {
             velocityX -= speed;
         }
         
         if(Input.GetButtonDown("up"))
         {
             velocityY = jumpForce;
         }
     }
     
     //Add Gravity
     velocityY -= gravity * Time.deltaTime;
     
     //Move Controller
     controller.Move(Vector3(velocityX, velocityY, 0) * Time.deltaTime);
 }