Unity crash when i use MasterServer.RegisterHost script

Now i learning how to make multiplayer game and i have problem when i use "MasterServer.RegisterHost(gameName, name, des)" Unity crash. Code (read comments):

 #pragma strict
 var gameName : String = "Kmcdiklomnd_Learning_Multiplayer";
 
 private var btnX : float;
 private var btnY : float;
 private var btnW : float;
 private var btnH : float;
 
 function Start(){
     btnX = Screen.width * 0.05;
     btnY = Screen.width * 0.05;
     btnW = Screen.width * 0.1;
     btnH = Screen.width * 0.1;
     
 }
 
 function startServer(){
     Network.InitializeServer(4, 25001, !Network.HavePublicAddress);
     // I use yield WaitForSeconds(2); to test then Unity crash.
     yield WaitForSeconds(2);
     // If i delete this \/ line of code everything works, so this line crash Unity
     MasterServer.RegisterHost(gameName, "Learning Multiplayer Game Name", "This is learning game");
 }
 
 //Messages
 function OnServerInitialized(){
     Debug.Log("Server initialized!");
 }

 // This function dont work because Unity crash before it start
 function OnMasterServerEvent(mse : MasterServerEvent){
     if(mse == MasterServerEvent.RegistrationSucceeded){
         Debug.Log("Registered Server!");
     }
 }
 
 function OnGUI () {
     if(GUI.Button(Rect(btnX, btnY, btnW, btnH), "Start Server")){
         Debug.Log("Starting Server");
         startServer();
     }
     
     if(GUI.Button(Rect(btnX, btnY * 1.2 + btnH, btnW, btnH), "Refresh Host")){
         Debug.Log("Refreshing");
     }
 }

So did anyone know how to fix it?