Text to speech virker ikke når den bliver kaldt fra en tråd

Jeg kan godt få text to speech til at virke når den bliver kaldt udenfor tråden (som den i form load)
men kalder jeg den inde fra tråden for jeg en error.

Selve source koden ser sådan ud:
Imports System.IO

Public Class Form1
    Inherits System.Windows.Forms.Form

    Dim Traad As Threading.Thread


#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer. 
    'Do not modify it using the code editor.
    Friend WithEvents SpkBtn As System.Windows.Forms.Button
    Friend WithEvents Speaker As AxHTTSLib.AxTextToSpeech
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Dim resources As System.Resources.ResourceManager = New System.Resources.ResourceManager(GetType(Form1))
        Me.Speaker = New AxHTTSLib.AxTextToSpeech
        Me.SpkBtn = New System.Windows.Forms.Button
        CType(Me.Speaker, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.SuspendLayout()
        '
        'Speaker
        '
        Me.Speaker.Enabled = True
        Me.Speaker.Location = New System.Drawing.Point(8, 8)
        Me.Speaker.Name = "Speaker"
        Me.Speaker.OcxState = CType(resources.GetObject("Speaker.OcxState"), System.Windows.Forms.AxHost.State)
        Me.Speaker.Size = New System.Drawing.Size(192, 120)
        Me.Speaker.TabIndex = 0
        '
        'SpkBtn
        '
        Me.SpkBtn.Location = New System.Drawing.Point(16, 144)
        Me.SpkBtn.Name = "SpkBtn"
        Me.SpkBtn.Size = New System.Drawing.Size(168, 40)
        Me.SpkBtn.TabIndex = 1
        Me.SpkBtn.Text = "Speak"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(216, 197)
        Me.Controls.Add(Me.SpkBtn)
        Me.Controls.Add(Me.Speaker)
        Me.Name = "Form1"
        Me.Text = "Form1"
        CType(Me.Speaker, System.ComponentModel.ISupportInitialize).EndInit()
        Me.ResumeLayout(False)

    End Sub

#End Region


    Private Sub SpkBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SpkBtn.Click
        Traad.Start()
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Speaker.Speak("Form has been loaded")
        Traad = New Threading.Thread(AddressOf Tal)
    End Sub

    Private Sub Tal()
        Speaker.Speak("hi there. How are you?")
    End Sub


End Class