Shoot a bullet

Hi, Ive been working on an FPS game and the script did not work, when i load the script it asked me for the API update and then if i press cancel there is always an error. Can someone please help me?
Here is the script.

var Bullet : Rigidbody;
var Spawn : Transform;
var BulletSpeed : float = 1000;
var fwd : Vector3;

function Start ()
{

}

function Update ()
{
fwd = transform.TransformDirection(Vector3.forward);
if(Input.GetMouseButtonDown(0))
{
Fire();
}
}

function Fire()
{
var bullet1 : Rigidbody;
bullet1 = Instantiate(Bullet, Spawn.position, Spawn.rotation) as Rigidbody;
bullet1.Rigidbody.useGravity = false;
bullet1.Rigidbody.AddForce(fwd * BulletSpeed, ForceMode.Impulse);
}

you are doing:

bullet1.Rigidbody.useGravity = false;
bullet1.Rigidbody.AddForce(fwd * BulletSpeed, ForceMode.Impulse); 

But bullet1 is rigidbody so no need to do bullet1.Rigidbody, also the variable name is not ‘Rigidbody’ it is ‘rigidbody’

try doing :

bullet1.useGravity = false;
bullet1.AddForce(fwd * BulletSpeed, ForceMode.Impulse);

@username