All the script stoped the update func when i lock the computer

Hi guys;
our company has an project which is about going to finish。But recently we found a problem. the unity version we used is 4.3.4.we found that when we lock the windows for a while and unlock it , the game begain at the time we locked the computer.And in the building setting inspector,we made the RunInBackground toggle checked. we write an test script as blew, when we locked the windows ,the count stopped counting.that means the update func has stopped working.we test this code at unity 4.1.2 it works well. but 4.3.4-4.6.4 does not work.we also tested it in unity 5.1.2 and it works…but if the whole project upgrade to UNITY5 ,the work we should do is huge.
so,is anyone has the same problem? and how can i fix it with no big change(or upgrade)?

using UnityEngine;
using System.Collections;

public class Test1 : MonoBehaviour {
	int[] t = new int[10];
	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
		Debug.LogError("Update");
		t[0]++;
	}
	void LateUpdate()
	{
		Debug.LogError("LateUpdate");
		t[1]++;
	}
	void OnDisable()
	{
		Debug.LogError("OnDisable");
	}
	void OnEnable()
	{
		Debug.LogError("OnEnable");
	}
	void FixedUpdate()
	{
		Debug.LogError("FixedUpdate");
	}
	void OnApplicationPause(bool pause)
	{
		Debug.LogError("OnApplicationPause (" + pause + ")");
	}
	void OnGUI()
	{
		Debug.LogError("OnGUI");
		t[2]++;

		GUILayout.Label(t[0]+", " + t[1] + ", " + t[2] + ": 	(" + Time.realtimeSinceStartup + ") 	(" + Time.time + ")");
		GUILayout.Label("Mouse Position: " + Input.mousePosition);
		GUILayout.Label("Screnn Size: " + Screen.width + " * " + Screen.height);
	}
}

“Run in background” in Windows means running while the game window is not the foreground/focused window. It doesn’t mean running while Windows is sleeping or has been locked or the OS is otherwise pausing or preventing applications from executing. Windows native lock suspends applications and there is nothing (simple) you can do to prevent that. All applications get suspended, not just Unity.