C Sharp Programm stürzt ab mit System.InvalidOperationException wurde nicht behandelt.

System.InvalidOperationException wurde nicht behandelt.
  Message="Ungültiger threadübergreifender Vorgang: Der Zugriff auf das Steuerelement Z8 erfolgte von einem anderen Thread als dem Thread, für den es erstellt wurde."  
  Source="System.Windows.Forms"  
  StackTrace:
       bei System.Windows.Forms.Control.get_Handle()
       bei System.Windows.Forms.Control.set_WindowText(String value)
       bei System.Windows.Forms.Control.set_Text(String value)
       bei System.Windows.Forms.Label.set_Text(String value)
       bei Superfinale.Anzeige.setcomdaten(String buffer) in C:\Users\Mirko\Documents\Visual Studio 2008\Projects\Superfinale\Superfinale\Anzeige.cs:Zeile 1074.
       bei Superfinale.Anzeige.serialPort1_DataReceived(Object sender, SerialDataReceivedEventArgs e) in C:\UsersNutzer\Documents\Visual Studio 2008\Projects\Superfinale\Superfinale\Anzeige.cs:Zeile 1090.
       bei System.IO.Ports.SerialPort.CatchReceivedEvents(Object src, SerialDataReceivedEventArgs e)
       bei System.IO.Ports.SerialStream.EventLoopRunner.CallReceiveEvents(Object state)
       bei System.Threading._ThreadPoolWaitCallback.WaitCallback_Context(Object state)
       bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       bei System.Threading._ThreadPoolWaitCallback.PerformWaitCallbackInternal(_ThreadPoolWaitCallback tpWaitCallBack)
       bei System.Threading._ThreadPoolWaitCallback.PerformWaitCallback(Object state)
  InnerException: 

private string buffer;
        
        public void setcomdaten(string buffer)
        {
                if (buffer != "")  
                {

                    //richTextBox1.Text += buffer + "\n"; 
                    //MessageBox.Show(buffer);

                    //MessageBox.Show("-" + buffer.Substring(14,5) + "- "+buffer); 
                    if (buffer.Substring(3, 2) == "2S")  
                        MessageBox.Show("Start Lauf-WK:" + buffer.Substring(11, 2) + "Lauf:" + buffer.Substring(13, 2) + "-\n");  
                    //if (buffer.Substring(20, 2) == "2S") 
                    //    MessageBox.Show("Start Lauf-WK:" + buffer.Substring(28, 2) + "Lauf:" + buffer.Substring(30, 2) + "-\n"); 
                    if (buffer.Substring(4, 4) == "1 1")  
                        MessageBox.Show("Bahn1 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "2 1")  
                        MessageBox.Show("Bahn2 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "3 1")  
                        MessageBox.Show("Bahn3 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "4 1")  
                        MessageBox.Show("Bahn4 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "5 1")  
                        MessageBox.Show("Bahn5 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "6 1")  
                        MessageBox.Show("Bahn6 00:" + buffer.Substring(14, 5) + "\n");  
                    if (buffer.Substring(4, 4) == "7 1")  
                        MessageBox.Show("Bahn7 00:" + buffer.Substring(14, 5) + "\n");  

                    if (buffer.Substring(4, 4) == "8 1")  
                    {

                        Z8.Text = "00:" + buffer.Substring(14, 5);  
                        //MessageBox.Show("Bahn8 00:" + buffer.Substring(14, 5) + "\n"); 
                    }
                }


            //}

        }
       
       

        public void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            buffer = serialPort1.ReadTo("");  
            
            setcomdaten(buffer);
                
            
        }