Problem rendering error text from Custom Validator

Private Sub btnWindowsLogin_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnWindowsLogin.Click
    Dim username As String = txtNetworkID.Text.Trim
    Dim password As String = txtPassword.Text

    If username.IsEmpty Then
        ErrorSummary.AddError("Please enter your NT Login", "WindowsLogin", Page)
    End If
    If password.IsEmpty Then
        ErrorSummary.AddError("Please enter your password", "WindowsLogin", Page)
    End If
    If Page.IsValid Then
        If Not AuthenticationService.ValidateActiveDirectoryLogin(username, password) Then
            ErrorSummary.AddError("The username or password you entered is incorrect", Page)
        ElseIf Not UserService.WindowsLoginExists(username) Then
            ErrorSummary.AddError("The NT Login entered is not associated with an account in the application", Page)
        Else
            'Get the user and validate the role, if the user is active, etc...

        End If
    End If
End Sub

Public Class ErrorSummary
    Inherits BaseValidator

    Public Sub New(ByVal message As String, ByVal validationGroup As String)
        MyBase.Text = message
        MyBase.ValidationGroup = validationGroup
        MyBase.IsValid = False
    End Sub

	Public Sub New(ByVal message As String)
		Me.New(message, String.Empty)
	End Sub

	Public Shared Sub AddError(ByVal message As String, ByVal page As Page)
		AddError(message, String.Empty, page)
	End Sub

	Public Shared Sub AddError(ByVal message As String, ByVal validationgroup As String, ByVal page As Page)
		Dim objError As New ErrorSummary(message, validationgroup)
		page.Validators.Add(objError)
	End Sub

	Protected Overrides Function EvaluateIsValid() As Boolean
		Return False
	End Function

End Class