Errors on Bullet script

Hi I have done a script for a bullet by using documentation of unity but I have a couple of errors. Here you have the code:

// - instantiates a explosion prefab when hitting a surface
// - then destroys itself

var explosionPrefab : Transform;

function OnCollisionEnter(collision : Collision) {
        // Rotate the object so that the y-axis faces along the normal of the surface
        var contact : ContactPoint = collision.contacts[0];
        var rot : Quaternion = Quaternion.FromToRotation(Vector3.up, contact.normal);
        var pos : Vector3 = contact.point;

        // Kill ourselves
        Destroy(gameObject);
        SendMessage ("ApplyDamage", 1);
        clone =     Instantiate(explosionPrefab, pos, rot);

        // Destroy the projectile
        Destroy (gameObject);
}

And here you have the errors:

The referenced script on this Behaviour is missing!
UnityEngine.Object:Instantiate(Object, Vector3, Quaternion)
ColisionBala:OnCollisionEnter(Collision) (at Assets/nuevo/ColisionBala.js:17)

And:

The referenced script on this Behaviour is missing!
UnityEngine.Object:Instantiate(Object, Vector3, Quaternion)
$:MoveNext() (at Assets/nuevo/EnemyRangedAttack.js:170)

And:

SendMessage ApplyDamage has no receiver!
UnityEngine.Component:SendMessage(String, Object)
ColisionBala:OnCollisionEnter(Collision) (at Assets/nuevo/ColisionBala.js:16)

Anyone can help me? I achieve the explosion but the player don't loose life >__<'

Thanks for all

Only destroy the gameObject once as the last thing in your script.

Edit: You should also use

collider.gameObject.SendMessage ("ApplyDamage", 1);

instead of just SendMessage, since you want to call ApplyDamage to the player and not the bullet itself. The player also needs a to have a component attached with a function of the signature:

function ApplyDamage(var v : Integer){
}

And the player also need to have the collider object on the same GameObject as the script with the ApplyDamage function.