ERROR Loading Script! WHAT'S WRONG??

Hello All,,

i'm a newbie in C# script

i have a problem here, i have download loading scripts it's works fine in original *.unitypackage File!, but it's always have an error, if the script i using it in my project. What's the problem??! i have checked the script manually and 'its same. No different at all. Can anybody help me? Thanks in advance (^-^)

here my scripts :

 using UnityEngine;
 using System.Collections;
 
 public class LoadingAWScript : MonoBehaviour 
 {
     public GUITexture LoadingTexture;
     public Texture[] LoadingTextures;
 
     private AsyncOperation loadscene;
     private float StreamProgress = 0.0f;
     // Use this for initialization
     void Start () 
     {
         LoadingTexture.texture = LoadingTextures[0];
         loadscene = Application.LoadLevelAsync("MainScene");
     }
     
     // Update is called once per frame
     void Update () 
     {
         StreamProgress  = loadscene.progress;
         if ( StreamProgress <= 0.0f)
             LoadingTexture.texture = LoadingTextures[0];
 
         if ( StreamProgress > 0.0f && StreamProgress <= 0.1f)
             LoadingTexture.texture = LoadingTextures[1];
 
         if ( StreamProgress > 0.1f && StreamProgress <= 0.2f)
             LoadingTexture.texture = LoadingTextures[2];
 
         if ( StreamProgress > 0.2f && StreamProgress <= 0.3f)
             LoadingTexture.texture = LoadingTextures[3];
             
         if ( StreamProgress > 0.3f && StreamProgress <= 0.4f)
             LoadingTexture.texture = LoadingTextures[4];
             
         if ( StreamProgress > 0.4f && StreamProgress <= 0.5f)
             LoadingTexture.texture = LoadingTextures[5];
             
         if ( StreamProgress > 0.5f && StreamProgress <= 0.6f)
             LoadingTexture.texture = LoadingTextures[6];
             
         if ( StreamProgress > 0.6f && StreamProgress <= 0.7f)
             LoadingTexture.texture = LoadingTextures[7];
 
         if ( StreamProgress > 0.7f && StreamProgress <= 0.8f)
             LoadingTexture.texture = LoadingTextures[8];
 
         if ( StreamProgress > 0.8f && StreamProgress <= 0.9f)
             LoadingTexture.texture = LoadingTextures[9];
 
         if ( StreamProgress > 0.9f && StreamProgress <= 1.0f)
             LoadingTexture.texture = LoadingTextures[10];
     }
 }