Multi-Threading Problem

Hej eksperter!

Jeg får denne fejl:
Illegal cross-thread operation: Control 'txtChat' accessed from a thread other than the thread it was created on.

Her er min frmMain:
Imports System
Imports System.String
Imports System.IO
Imports System.Net.Sockets
Imports System.Threading

Public Class frmMain
    Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Hide()
        frmConnect.ShowDialog()
        Chat.Write("Info", "System", "Main Form Loaded...")

    End Sub

    Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
        Chat.Write("Chat", "Me", txtSend.Text)
    End Sub
End Class
Class Chat
    Public Shared Sub Write(ByVal Type As String, ByVal Sender As String, ByVal ChatText As String)
        With frmMain.txtChat
            .SelectionStart = Len(.Text)
            Select Case Type
                Case "Chat"
                    .SelectionColor = Color.Black
                Case "Info"
                    .SelectionColor = Color.Green
                Case "System"
                    .SelectionColor = Color.Red
            End Select
            If Not Len(.Text) = 0 Then
                .AppendText(vbCrLf)
            End If
            .AppendText("[22:22]<")
            .SelectionStart = Len(.Text)
            .SelectionFont = New Font(.Font.Name, .Font.Size, FontStyle.Bold)
            .AppendText(Sender)
            .SelectionStart = Len(.Text)
            .SelectionFont = New Font(.Font.Name, .Font.Size, FontStyle.Regular)
            .AppendText("> " & ChatText)
        End With
    End Sub
End Class
Class ChatClient
    Public Sub Main()
        Call Chat.Write("System", "System", "Connecting to " & frmConnect.txtIp.Text & ":50000")
        Dim client As TcpClient = New TcpClient(frmConnect.txtIp.Text, "50000")
        Dim wrt As StreamWriter = New StreamWriter(client.GetStream)
        Call (New Thread(AddressOf (New Reader(client)).Run)).Start()
        Dim line As String
        line = frmMain.txtSend.Text
        While Not (line Is Nothing)
            wrt.WriteLine("Chat<|||>" + line) '<|||> tagget bruger jeg til at splitte ting med på serveren...
            wrt.Flush()
            frmMain.txtSend.Text = ""
        End While
        wrt.WriteLine("Quit")
        wrt.Flush()
        wrt.Close()
        client.Close()
    End Sub
End Class

Class Reader
    Private rdr As StreamReader

    Public Sub New(ByVal cli As TcpClient)
        rdr = New StreamReader(cli.GetStream)
    End Sub

    Public Sub Run()
        Try
            Dim line As String
            line = rdr.ReadLine
            While Not (line Is Nothing)
                Chat.Write("Chat", "System Tester", line)
                line = rdr.ReadLine
            End While
        Catch e As Exception
            ' nothing
        End Try
    End Sub
End Class

Her er min frmConnect:
Imports System.Threading

Public Class frmConnect

    Private Sub btnConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click
        Me.Hide()
        frmMain.Show()
        Call (New Thread(AddressOf (New ChatClient()).Main)).Start()
    End Sub
End Class

VB.Net 2005 Express markerer 2. og 4. linie her:
Class Chat
    Public Shared Sub Write(ByVal Type As String, ByVal Sender As String, ByVal ChatText As String)
        With frmMain.txtChat
            .SelectionStart = Len(.Text)


Hvad gør jeg galt?