RS232 Can't handle VB2008

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VB8

VB

Hi to all !
I wrote a code in VB2008/NET2.0,after a problem with my operating system i re-wrote this code.I'm using this code in order to communicate my Atmel board with my PC and display some graphic data via NI Measurement Studio.

The problem is,that now i can't make it communicate with Atmel,can someone of you tell me where is the error ?

The program is running but does not reads data from RS232,on the other hand i use Hyper Terminal to test my connection and it works perfect...
I have also try to different version of .NET (2.0 & 3.0).
Another question is that after some executions of this code my O.S. crashes (WinXP Home).
Is there any solution for these two problems?
Thank's a lot for your time! :-D :-D
-----------------CODE-----------------------------

Imports System.IO.Ports.SerialPort
Imports System.Windows.Forms.Control
Imports System.Windows.Forms.Form

Public Class Form1

    Public Delegate Sub myDelegate()

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If SerialPort1.IsOpen Then
            SerialPort1.Close()
        End If

        Try
            With SerialPort1
                .PortName = "Com1"
                .BaudRate = 9600
                .Parity = IO.Ports.Parity.None
                .DataBits = 8
                .StopBits = IO.Ports.StopBits.One
                .ReceivedBytesThreshold = 1
            End With
            SerialPort1.Open()
        Catch ex As Exception
        End Try
    End Sub

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        Me.Dispose()
        Try
            SerialPort1.Close()
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

    End Sub

    Private Sub DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs)

        TextBox1.Invoke(New myDelegate(AddressOf updateTextBox), New Object() {})
    End Sub

    Public Sub updateTextBox()
        Dim input As String
        input = SerialPort1.ReadExisting
        If input = "A" Then alive()
        If input = "T" Then tank()
        If input = "G" Then gauge()
        If input = "O" Then outemp()
        If input = "B" Then boiler()
        If input = "W" Then water()

        'Try

        'Catch ex As Exception

        'End Try
        With TextBox1
            .Font = New Font("Garamond", 12.0!, FontStyle.Bold)
            .AppendText(SerialPort1.ReadLine)
            .ScrollToCaret()
        End With
    End Sub

    Sub tank()
        Dim tankval As Integer
        tankval = Integer.Parse(SerialPort1.ReadLine.Trim())
        Tank1.Value = tankval
        If tankval < 200 Then
            Beep()
            Led3.Value = True
            Led2.Value = False
            Led1.Value = False
        ElseIf tankval > 200 And tankval < 750 Then
            Led3.Value = False
            Led2.Value = True
            Led1.Value = False
        ElseIf tankval > 750 Then
            Led3.Value = False
            Led2.Value = False
            Led1.Value = True
        End If

    End Sub
    Sub water()
        Dim tankval1 As Integer
        tankval1 = Integer.Parse(SerialPort1.ReadLine.Trim())

        Tank2.Value = tankval1
        If tankval1 < 300 Then
            Beep()
            Led6.Value = True
            Led5.Value = False
            Led4.Value = False
        ElseIf tankval1 > 300 And tankval1 < 4500 Then
            Led6.Value = False
            Led5.Value = True
            Led4.Value = False
        ElseIf tankval1 > 4500 Then
            Led6.Value = False
            Led5.Value = False
            Led4.Value = True
        End If

    End Sub

    Sub gauge()
        Dim gauge As Double
        gauge = Integer.Parse(SerialPort1.ReadLine.Trim())
        If gauge < 0 Then gauge = 0
        gauge = gauge / 0.434 / 100
        Gauge1.Value = gauge
    End Sub
    Sub outemp()
        Dim temper As Integer
        temper = Integer.Parse(SerialPort1.ReadLine.Trim())

        Thermometer1.Value = temper
    End Sub

    Sub boiler()
        Dim boiler As Integer
        boiler = Integer.Parse(SerialPort1.ReadLine.Trim())

        Thermometer2.Value = boiler
    End Sub

    Sub alive()
        SerialPort1.Write("L")
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        SerialPort1.Close()
        Me.Close()
    End Sub
End Class

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