Error, I have no idea why :(

I'm getting this error,

 "InvalidCastException: Cannot cast from source type to destination type.
 Player.Update () (at Assets/Mine/Scripts/Player.js:30)"

but I don't know what it means or why it's happenning. this is my script:

 #pragma strict
 
 var range : float;
 var bombs : int = 1;
 var speed : int = 1;
 var fire : int = 1;
 var bomb : Transform;
 var bombSpawner : GameObject;
 var health : int = 1;
 var Distance : float;
 var MaxDistance : float = 1.6;
 
 function Update () 
 {
     MaxStats ();
     Speed ();
     
     if (health < 1)
     Destroy (gameObject);
     
     Debug.DrawRay(transform.position, (transform.forward + Vector3.down).normalized * range, Color.red);
     
     if (Input.GetMouseButtonDown(0) && bombs >=1)
     {
         var Hit : RaycastHit;
         if (Physics.Raycast(transform.position, (transform.forward + Vector3.down).normalized , Hit, range))
         {
             if(Hit.collider.gameObject.tag == "Ground")
             {
             var bomb : Transform = Instantiate (bomb, Hit.collider.gameObject.transform.position, Quaternion.identity);
             bomb.gameObject.transform.Translate(0,0.77,0);
             }
         }
     }
 }