Mouse Lock script doesn't work once built, help?

script for mouse lock doesnt work once its built, but works in editor... using UnityEngine; using System.Collections;

 public class LockCursor : MonoBehaviour {
 
     void Start () {
         // Start out in paused mode in web player
         if (Application.platform == RuntimePlatform.OSXWebPlayer || Application.platform == RuntimePlatform.WindowsWebPlayer) {
             SetPause(true);
         } else {
             SetPause(false);
             Screen.lockCursor = true;
         }
     }
 
     void OnApplicationQuit () {
         Time.timeScale = 1;
     }
 
     void SetPause (bool pause) {
         Input.ResetInputAxes();
         DidPause(pause);
         
         transform.position = Vector3.zero;
         
         if (pause) {
             Time.timeScale = 0;
             transform.position = new Vector3 (.5f, .5f, 0);
             guiText.anchor = TextAnchor.MiddleCenter;
         } else {
             guiText.anchor = TextAnchor.UpperLeft;
             transform.position = new Vector3(0, 1, 0);
             Time.timeScale = 1;
         }
     }
 
     void DidPause (bool pause) {
         if (pause) {
             // Show the button again
             guiText.enabled = true;
             guiText.text = "Click to start playing";
         } else {
             // Disable the button
             guiText.enabled = true;
             guiText.text = "Escape to show the cursor";
         }
     }
 
     void OnMouseDown () {
         // Lock the cursor
         Screen.lockCursor = true;
     }
 
     private bool wasLocked = false;
 
     void Update () {
         if (Input.GetMouseButton(0))
             Screen.lockCursor = true;
         
         // Did we lose cursor locking?
         // eg. because the user pressed escape
         // or because he switched to another application
         // or because some script set Screen.lockCursor = false;
         if (!Screen.lockCursor && wasLocked) {
             wasLocked = false;
             SetPause(true);
         // Did we gain cursor locking?
         } else if (Screen.lockCursor && !wasLocked) {
             wasLocked = true;
             SetPause(false);
         }
     }
 }