Strange Problem with mdi tabcontrol

[edwinho]

Public Class Form1
       Dim WebBrowserA, WebBrowserB As New WebBrowser

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    ' WebPage   Inside the Tabcontrol
         Dim MyFristPage As New Form
        MyFristPage.Size = New Point(500, 500)
        MyFristPage.Location = New Point(500, 500)
        MyFristPage.Text = "Loading"
        TabControl1.TabPages.Add(MyFristPage)
        WebBrowserA.Dock = DockStyle.Fill
        WebBrowserA.Parent = MyFristPage
        WebBrowserA.Navigate("http://www.cyberspacers.com/games/Piano.swf")
     
           
' Webpage on MainForm
        WebBrowserB.Parent = Me
        WebBrowserB.Top = Me.Top - 50
        WebBrowserB.Left = Me.Width / 2
        WebBrowserB.Width = Me.Width / 2
        WebBrowserB.Height = Me.Height - 50
       
        WebBrowserB.Navigate("http://www.cyberspacers.com/games/Piano.swf")
   
    End Sub

    Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
        TabControl1.Width = Me.Width / 2
        WebBrowserB.Left = Me.Width / 2
        WebBrowserB.Width = Me.Width / 2
    End Sub

I have problem to play the piano swf inside the TabControl1 (WebBrowserA), but i can play piano swf within the main form (WebBrowserB).

Anyone know why, and the method to solve it to play at tabcontrol1