Lock Cursor problem in Unity 3D 5.

The error is telling you that Cursor.lockState is not a bool but an enum of type CursorLockMode. Looking in the unity documentation you can see that CursorLockMode can have 3 values, None, Locked, and Confined. Therefore use the following line

 Cursor.lockState = CursorLockMode.Locked;

http://docs.unity3d.com/500/Documentation/ScriptReference/CursorLockMode.html

https://www.youtube.com/watch?v=2bWoRTRT_DU

 using UnityEngine;
 using System.Collections;
 
 public class HideLockCursorA : MonoBehaviour
 {
 void Start ()
   {
     Cursor.lockState = CursorLockMode.Locked;
     Cursor.visible = false;
   }
                   void Update ()
             {
                     Cursor.lockState = CursorLockMode.Locked;
                     Cursor.visible = false;
             }
 }

Here is what I did for my lock cursor script

 function Start ()
     {
     Screen.lockCursor = true;
     UnityEngine.Cursor.visable = false;
     }

You have to have it in update at this time due to a bug in unity where it loses focus. Hopefully they will fix this someday....Unfortunately currently the only way which is bad for performance is this way from what I can tell. You could detect and create an void OnFocus but that would be OS dependent :( In other words it would be different if it's a Mac/Phone/Windows/ect ect. So this is the only practical solution for when you lose focus(basically alt+tab) constantly.

 void Update()
     {
         if (Cursor.lockState != CursorLockMode.Locked)
         {
             Cursor.lockState = CursorLockMode.Locked;
             Cursor.visible = false;
         }
     }

Well, the script that I used was this:

 void Update()
 {
         //Mouse lock and confine
         Cursor.visible = false;
         Cursor.lockState = CursorLockMode.Locked;
         Cursor.lockState = CursorLockMode.Confined;
 
 //and to unlock it is this:
         Cursor.lockState = CursorLockMode.None;
         Cursor.visible = true;
 }

I hope this helps!