'Object reference not set to an instance of an object' error

Hi everyone,
I have this script where when you press Space, that slows down time (bullet time). The thing is that I want the speed of the character increased a little bit when the time slows down, but when I press Space it gives me this error:
‘Object reference not set to an instance of an object’ (and the character slows down like everything else in the scene).

Does the problem come from the bullet time?
And is it possible or easier to slow down every objects in the scene but the player instead?

Here’s the script:

    var currentBulletTimer : float = 0;
    var bulletTimeAllowed : float = 30.0;

	//private var speed : float = 0;
    private var speed : int = 0;
	//variable to access the C# script  
	private var csScript : Controller2D;  
	function Awake()  
    //Get the CSharp Script  
    csScript = this.GetComponent("Controller2D");  

    function Update ()
    if (Input.GetKeyDown(KeyCode.Space)) {
    //if (Input.GetButtonDown ("Fire2")) {
    if (Time.timeScale == 1.0)
    Time.timeScale = 0.3;
    Time.timeScale = 1.0;
    //Time.fixedDeltaTime = 0.02 * Time.timeScale;
    if (Time.timeScale == 0.3)
    currentBulletTimer += Time.deltaTime;
    //increase speed
    speed = Controller2D.walkSpeed = 30;
    if ( currentBulletTimer > bulletTimeAllowed )
    currentBulletTimer = 0;
    Time.timeScale = 1.0;

(The problem doesn’t come from the Controller2D C# script since I put it in the Standard Assets folder.)
Thanks for any help I can get!

Hi the problem is ,in this line you have used Controler2D

speed = Controller2D.walkSpeed = 30;

but you have not defined it so you might wanna change it to

speed = 30;
csScript.walkSpeed = speed;

And dont use GetComponent(String) its obsolute


 csScript = transform.GetComponent.<Controller2D>();