C# 超级线程问题！！！

 private void Form1_Load(object sender, EventArgs e)
        {
            this.textBoxSend.Focus();
            Serial.OpenPort("COM3:", 9600, 0, 8, 1);
            PortOpen = true;
            Receive = true;           
            ThreadPool.QueueUserWorkItem(new WaitCallback(SerialReceive), 0);           
            this.isLoad = true;
            button1.Text = "Close";           
        }
   public void SerialReceive(Object a)
        {
            if (isLoad)
            {
                Thread.Sleep(800);
            }
            byte[] buf;            buf = new byte[1];
            int bytesRead = 0;
            int i;
            this.code = "";
            while (Receive)
            {
                if (Serial.Opened)
                {
                    bytesRead = Serial.ReadPort(1, buf);
                    if (bytesRead > 0)
                    {
                        for (i = 0; i < bytesRead; i++)
                        {
                            GetDate(Convert.ToChar(buf[i]).ToString());
                        }
                    } 
                }
            }
            
            this.isLoad = false;
        }
  private void GetDate(string a)
        {
            if (this.InvokeRequired)
            {
                this.Invoke(new GetDateDelegate(GetDate), new object[] { a });
                return;
            }
            this.code += a;
            if (a == "\n")
            {
                this.textBoxSend.Text = "";
                    this.data = this.code.Substring(0, this.code.Length-2);                    
                    //Thread.Sleep(Int32.Parse(Global.Timer) * 500);
                    //this.SaveData(this.code);
                    Global.DataValue = data;
                    //Thread fThread = new Thread(new ThreadStart(SaveData));                    //fThread.Start();
                    this.textBoxSend.Text = data;
                    //fThread.Abort();
                   //Thread thread = new ThreadStart(SaveData);
                   //thread.Start();                    int success = sw.CodeInfoInsert(this.data);//通过web服务调用的web方法。
                    if (success == 1)
                        WriteWarning(data);
                    else if (success == 2)
                        WriteWarning("NOREAD");
                    else
                        WriteWarning("NoNet");
                                 
            }
            textBoxReceive.Text += a;        }
上面代码为什么只有在第一次执行的时候能够保存进数据库，第一次后都是失败值返回！！！难道是线程没控制！？！有望达人讲解！！！