All of your UI code needs to be on one thread.  That's probably the problem.

John Saunders

You seem to be breaking the golden rule of threading in Windows Forms
applications:  never touch UI objects from any thread other than the thread
on which they were created.

This article discusses how to use multiple threads safely (i.e. without
breaking this rule) in a Windows Forms application:

 http://msdn.microsoft.com/msdnmag/issues/03/02/Multithreading/

There's also a good discussion here:

 http://www.yoda.arachsys.com/csharp/threads/winforms.shtml

In fact if you plan on doing any multithreaded development in Windows Forms,
I'd recommend you read all of Jon Skeet's threading articles:

 http://www.yoda.arachsys.com/csharp/threads/

You really need to understand pretty much all of the topics he covers in
these articles before you'll be able to write reliable multithreaded code in
.NET.

Charles,

Did I ever showed you this sample of my.

Before you become confuse about it, be aware this that it shows two the same
forms (form2), one with multithreading and one without.

Normally I send only the Google link, however I have the idea Google has
since today shorten his newsgroup service and is it not possible anymore to
show only one message.

\\\needs  on form 1  one button and three textboxes
Private WithEvents frm1 As Form2
Private Delegate Sub Frm1Handler(ByVal message As String)
Private WithEvents frm2 As Form2
Private MyThread As System.Threading.Thread
Private Sub Form1_Load(ByVal sender As Object, _
          ByVal e As System.EventArgs) Handles MyBase.Load
       Dim timer1 As New System.Windows.Forms.Timer
       AddHandler timer1.Tick, AddressOf mytimer1
       TextBox1.Text = "0"
       timer1.Enabled = True
       timer1.Interval = 400
       Dim timer2 As New System.Windows.Forms.Timer
   End Sub
   Private Sub mytimer1(ByVal sender As Object, _
     ByVal e As System.EventArgs)
       TextBox1.Text = (CInt(TextBox1.Text) + 1).ToString
       DirectCast(sender, System.Windows.Forms.Timer).Enabled = True
   End Sub
   Private Sub Button1_Click(ByVal sender As System.Object, _
   ByVal e As System.EventArgs) Handles Button1.Click
       frm1 = New Form2
       frm1.itstop = Me.Top
       frm1.itsleft = Me.Left + 200
      AddHandler frm1.ready, AddressOf Frm1Ready
       frm1.Text = "Extra thread"
       MyThread = New System.Threading.Thread(AddressOf frm1.Show)
       MyThread.Start()
       frm2 = New Form2
       frm2.itstop = Me.Top
       frm2.itsleft = Me.Left + 400
       frm2.Text = "In own thread"
       AddHandler frm1.ready, AddressOf Frm2Ready
       frm2.Show()
   End Sub
   Private Sub Frm1Ready(ByVal message As String)
       Me.BeginInvoke(New Frm1Handler(AddressOf Frm1HandlerSub), New
Object() {message})
   End Sub
   Private Sub Frm1HandlerSub(ByVal message As String)
       TextBox2.Text = message
       frm1.Close()
       MyThread.Abort()
   End Sub
   Private Sub frm2ready(ByVal message As String)
       TextBox3.Text = message
       frm2.Dispose()
   End Sub
Private Sub Form1_Closing(ByVal sender As Object, _
   ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
       MyThread.Abort()
End Sub
///
\\\Needs a form2 with one textbox
   Friend Event ready(ByVal message As String)
   Friend itstop As Integer
   Friend itsleft As Integer
   Private Sub Form2_Activated(ByVal sender As Object, _
   ByVal e As System.EventArgs) Handles MyBase.Activated
       Me.Left = itsleft
       Me.Top = itstop
       Me.BringToFront()
       Dim timenext As DateTime = Now.Add(TimeSpan.FromSeconds(10))
       Do While timenext > Now
           TextBox1.Text = Now.TimeOfDay.ToString
           Application.DoEvents() 'to show the time
           Threading.Thread.Sleep(50)
           Me.Opacity -= 0.004
       Loop
       RaiseEvent ready(Now.TimeOfDay.ToString)
   End Sub
   Private Sub Form2_Closing(ByVal sender As Object, ByVal _
   e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
       e.Cancel = True
   End Sub
///

I hope this helps a little bit?

Cor