Network game. Server not responding(stuck).

So, my network game works fine for a while then for some strage reason the server gets stuck(clicking on it says the game is not responding). If i disconnect the client the server loads the main menu fine and works ok again.

Here is the spawn code for the crate:

using UnityEngine;
using System.Collections;

public class CrateSpawner : MonoBehaviour {


	public float spawnTimer = 10.0f;

	

	public void SpawnCrates()
	{
			if (Network.isServer)
		    {

		
				Network.Instantiate (Resources.Load ("Prefabs/crate2"), this.transform.localPosition, this.transform.rotation, 0);
		    }
	}	


	void Update () {

		if (spawnTimer <= 0) {
		
			SpawnCrates();
			spawnTimer = 60.0f;
				}

		else {
			spawnTimer -= Time.deltaTime; 

	}
}

}