C#

public partial class Picaxecomm : Form
    {

        private Thread scanThread;
        private Thread writeThread;
        private String line;
        private SerialPort serialPort;
        private Boolean start;
        private AutoResetEvent autoEvent;

        public Picaxecomm()
        {
            InitializeComponent();
            serialPort = new SerialPort();
            initializePort();
            autoEvent = new AutoResetEvent(false);
            scanThread = new Thread(new ThreadStart(readPic));
            writeThread = new Thread(new ThreadStart(writeDisp));
        }
         /**
         * Initializes the port with the desired parameters for the communication with the PICAXE chip.
         */
        public void initializePort()
        {
            serialPort.PortName = "COM5";
            serialPort.BaudRate = 4800;
            serialPort.DataBits = 8;
            serialPort.ReadTimeout = 100;
            serialPort.Open();
            serialPort.DtrEnable = true;
        }

        /*
         * Just a button, then I know that the program at least starts succesfully.
         */
        private void knapp_Click(object sender, EventArgs e)
        {
            if (start == false)
            {
                writeThread.Start();
                scanThread.Start();
                start = true;
            }
        }
        /**
         * The scanThrad goes in a loop when scanning the port.   
         * The autoevent signals the writeThread that the scanThread actually has got something and written it to
         * the line string. 
         */
        public void readPic()
        {
            
            try
            {
                int i = serialPort.ReadByte();
                lock (this) //I have tried to remove this, but doesn't make any difference. 
                {
                    line = Convert.ToString(i);
                }
                autoEvent.Set();
            }

            catch (TimeoutException)
            {
                
            }
            Thread.Sleep(50);
            readPic();
            
            
        }

        /**
         * This is where the writeThread works. Made an if/else thing around the invoke, just to be sure,
         * as it seems there is something with another thread than the the one that made the display writng it(killer
         * sentence;))
         */
        public void writeDisp()
        {
            autoEvent.WaitOne(); //Got the signal from the scanThread. Let's write the display.
            if (display.InvokeRequired)
           {
               display.Invoke(new MethodInvoker(delegate() { setDispText(); }));
           }
           else
           {
               setDispText();
           }
        }

        /**
         * Looks like the program stops somewhere in this method
         */
        public void setDispText()
        {
            display.Text = line;
            serialPort.DiscardInBuffer();
            writeDisp();
        }

        private void Picaxecomm_Load(object sender, EventArgs e){} //Didn't compile without. Whatever.
        }
}