Is it a bug?

Hello i have a problem with Unity 4.0.0 . When i play the AngryBots project or even when i make my own char with simple walking script it automatically walk with pressing any button. I try uninstall the unity, i try with older unity, i delete even from registry, still the same thing. Why, is it a bug, am i doing something wrong?

 var speed = 6.0;  
  
 var jumpSpeed = 8.0;   
 
 var gravity = 20.0;   
 
 
 private var moveDirection = Vector3.zero;   
 
 private var grounded : boolean = false;   
 
 
 function FixedUpdate() {   
 
 if (grounded) {   
 
 // We are grounded, so recalculate movedirection directly from axes   
 
 moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, 0);   
 
 moveDirection = transform.TransformDirection(moveDirection);   
 
 moveDirection *= speed;  
 
 
 if (Input.GetButton ("Jump")) {  
 
 moveDirection.y = jumpSpeed;   
 
 }  
  
 } // Apply gravity   
 
 moveDirection.y -= gravity * Time.deltaTime;  
 
 
 // Move the controller   
 
 var controller : CharacterController = GetComponent(CharacterController);  
 
 var flags = controller.Move(moveDirection * Time.deltaTime);  
  
 grounded = (flags & CollisionFlags.CollidedBelow) != 0;  
 
 }   
 
 
 @script RequireComponent(CharacterController)  

I am using this script for all my walking chars and it works, but now its walking automatically.

Please help, and thank you!