Bing Maps i problem z pushpinami.

Witam serdecznie.

Piszę aplikacje, która pobiera sobie z telefonu współrzędne GPS a następnie co 3 sekundy wyświetla pina na mapie.
Wszystko fajnie działa, dopóki nie podłącze drugiego klienta. Dostaję wtedy błąd:

 An unhandled exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll

Additional information: Exception has been thrown by the target of an invocation.

Jeśli nie wywołuję wątku "map", a tym samym nie umieszczam pinów na mapie, to wszystko działa.

Przyznam szczerze, że dopiero odkrywam wątki więc proszę o wyrozumiałość i pomoc.

Oto kod:

    namespace WpfApplication1
    {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private TcpListener tcpListener;
        private Thread listenThread;
        private int pinCounter = -1;
        private Pushpin[] pinList = new Pushpin[10];
        string c;
        string[] words;      
        

        public MainWindow()
        {
            InitializeComponent();

        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            ResizeMode = ResizeMode.NoResize;

            this.tcpListener = new TcpListener(IPAddress.Any, 7);
            this.listenThread = new Thread(new ThreadStart(ListenForClients));
            this.listenThread.Start();
        }

        private void ListenForClients()
        {
            this.tcpListener.Start();

            while (true)
            {
                //blocks until a client has connected to the server
                TcpClient client = this.tcpListener.AcceptTcpClient();

                //create a thread to handle communication 
                //with connected client
                
                Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
                clientThread.Start(client);
            }
        }

        private void map()
        {
             this.Dispatcher.BeginInvoke((ThreadStart)delegate()
                    {
                            for (int i = 0; i < 10; i++)
                            {
                                if (pinList[i] != null)
                               {
                                   if (Map.Children.Count != 0)
                                   {
                                       var pushpin = Map.Children.OfType<Pushpin>().FirstOrDefault(p => ("locationPushpin"+pinCounter).Equals(p.Tag));

                                       if (pushpin != null)
                                       {
                                           Map.Children.Remove(pushpin);
                                       }
                                   }
                                   Map.Children.Add(pinList[i]);

                                }
                            }
                     });
        }

        private void HandleClientComm(object client)
        {
           
            TcpClient tcpClient = (TcpClient)client;
            NetworkStream clientStream = tcpClient.GetStream();
            byte[] message = new byte[200];
            int bytesRead;
            pinCounter++;

            while (true)
            {
                try
                {
                    //blocks until a client sends a message
                    bytesRead = clientStream.Read(message, 0, 200);
                }
                catch
                {
                    //a socket error has occured
                    break;
                }

                if (bytesRead == 0)
                {
                    tcpClient.Close();
                    break;
                }


                c = Encoding.ASCII.GetString(message, 0, bytesRead);
                words = c.Split('\n');

                this.Dispatcher.BeginInvoke((ThreadStart)delegate()
                {

                    Pushpin pin = new Pushpin();

                        pinList[pinCounter] = pin;

                        pinList[pinCounter].Tag = "locationPushpin" + pinCounter.ToString();

                        pinList[pinCounter].Location = new Location(Double.Parse(words[1], CultureInfo.InvariantCulture), Double.Parse(words[2], CultureInfo.InvariantCulture));

                        textBox1.Text = "Coords: " + words[1] + ", " + words[2];

                        ToolTipService.SetToolTip(pinList[pinCounter], words[0] + "\n" + words[1] + "\n" + words[2] + "\n" + pinCounter.ToString());

                        Thread mapThread = new Thread(new ThreadStart(map));
                        mapThread.Start();
                    }
                
                    );
            }
            
        }
       

        private void button1_Click(object sender, RoutedEventArgs e)
        {

            Map.ZoomLevel += 1;
        }

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            
            Map.ZoomLevel -= 1;
        }


    }
    }