.net2003的bug?

Page_load的代码:        Me.FindControl("myForm").Controls.Add(CreateTextBox(100, 50, "txtAAAA", "txtAAAA", "", 0, 0, 1))        If IsPostBack = True Then
            Dim tx As System.Web.UI.WebControls.TextBox
            tx = CType(Me.FindControl("txtAAAA"), System.Web.UI.WebControls.TextBox)
            tx.BackColor = Color.Red
            tx.Text = "AAAA"
        End If