That error would indicate to me that the method hasn't been declared. LevelLoadFade isn't a native function in Unity - it's probably part of the FPS Tutorial.
Here's a script from one of the wiki's... I trigger it to fade a loading screen in, I wait for that to finish, then I trigger the Application.LoadLevel (which has the same image on the other side but fades out).
// FadeInOut
//
//--------------------------------------------------------------------
// Public parameters
//--------------------------------------------------------------------
public var fadeOutTexture : Texture2D;
public var fadeSpeed = 0.3;
var drawDepth = -1000;
//--------------------------------------------------------------------
// Private variables
//--------------------------------------------------------------------
private var alpha = 1.0;
private var fadeDir = -1;
//--------------------------------------------------------------------
// Runtime functions
//--------------------------------------------------------------------
//--------------------------------------------------------------------
function OnGUI(){
alpha += fadeDir * fadeSpeed * Time.deltaTime;
alpha = Mathf.Clamp01(alpha);
GUI.color.a = alpha;
GUI.depth = drawDepth;
GUI.DrawTexture(Rect(0, 0, Screen.width, Screen.height), fadeOutTexture);
if (alpha<0.01) {
Destroy(gameObject,0);
}
}
//--------------------------------------------------------------------
function fadeIn(){
fadeDir = -1;
}
//--------------------------------------------------------------------
function fadeOut(){
fadeDir = 1;
}
function Start(){
alpha=1;
fadeIn();
}