Error in script to make a monster shoot against the player

I have done a function to use in a script for one of my monsters (on my 3d plattaform game) and I have a problem with it, when I test the game, it crashes with unity and I have to terminate the process through Ctrl+alt+del. Do you have any idea what is going wrong?

Here you have the code (I have a rigidbody on unity too to use it as bullet, and its passed through the editor to the script):

var projectile : Rigidbody;

function Shoot ()
            // Instantiate the projectile at the position and rotation of this transform
        var clone : Rigidbody;
        clone = Instantiate(projectile, transform.position, transform.rotation);

        // Give the cloned object an initial velocity along the current
        // object's Z axis
        clone.velocity = transform.TransformDirection (Vector3.forward * 10);
// yield for one frame

You put yield outside of your infinite loop. Put in before the curly brace instead of after. If you line up your curly braces better, you'll have a better chance of catching mistakes yourself.