Network Game not working.

When I test my networked game in Unity, everything works fine. However when I build it, I get nothing but a blank screen. Anyone know whats wrong?

Here's my script: var playerPrefab:GameObject; var spawnObject:Transform; var gameName:String = "Yung_Pharaoh_Test_Network";

 private var refreshing:boolean;
 private var hostData:HostData[];
 
 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(32, 25001, !Network.HavePublicAddress);
     MasterServer.RegisterHost(gameName,"Network Test","This is a test");    
 }
 
 function refreshHostList(){
     MasterServer.RequestHostList(gameName);
     refreshing = true;
 }
 
 function Update(){
     if(refreshing){
         if(MasterServer.PollHostList().Length > 0){
             refreshing = false;
             Debug.Log(MasterServer.PollHostList().Length);
             hostData = MasterServer.PollHostList();
         }
     }
 }
 
 
 function spawnPlayer(){
     Network.Instantiate(playerPrefab, spawnObject.position, Quaternion.identity, 0);
 }
 
 //Messages
 function OnServerInitialized(){
     Debug.Log("Server Initialized");
     spawnPlayer();
 }
 
 function OnConnectedToServer(){
     spawnPlayer();
 }
 
 function OnMasterServerEvent(mse:MasterServerEvent){
     if(mse == MasterServerEvent.RegistrationSucceeded){
         Debug.Log("Registered Server");
     }
 }
 
 //GUI            
 function OnGUI(){
     if(!Network.isClient && !Network.isServer){
         if(GUI.Button(Rect(btnX, btnY, btnW, btnH), "ST4RT_S3RV3R")){
             Debug.Log("Starting Server");
             startServer();
         }
         
         if(GUI.Button(Rect(btnX, btnY * 1.2 + btnH, btnW, btnH), "R3FR3SH_HØSTS")){
             Debug.Log("Refreshing");
             refreshHostList();
         }
         if (hostData){
             for(var i:int = 0; i < hostData.length; i++){
                 if(GUI.Button(Rect(btnX * 1.5 + btnW, btnY * 1.2 +(btnH * i), btnW * 3, btnH * 0.5), hostData[i].gameName)){
                     Network.Connect(hostData[i]);
                 }
             }
         }
     }
 }