Erro ao colocar o User Control no Visual Studio 2010

Pessoal.

Fiz um User Control para testes que cria uma nova propriedade para um Textbox no qual este colocará a primeira letra de cada palavra em maiusculo.

O User Control é criado normalmente mas quando vou criar um projeto e colocar este User Control no Visual Studio aparece a tela com o erro: Code genaration for Property 'CharacterCasing' failed. Error was: 'The value -1' is not a valid value for the enum 'ExtendedCharacterCasing'.

Como resolvo isso?

O meu código é:

Designer:

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class TextBoxEx
Inherits System.Windows.Forms.TextBox

'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.
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
components = New System.ComponentModel.Container()
'Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
End Sub

Classe:

Imports System.ComponentModel

Public Class TextBoxEx : Inherits TextBox
Public Sub New()
MyBase.New()

' This call is required by the designer.
InitializeComponent()

' Add any initialization after the InitializeComponent() call.

End Sub

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

Private _casingSelected As ExtendedCharacterCasing
Public Enum ExtendedCharacterCasing
Normal
Upper
Lower
Proper
End Enum

<DefaultValue(ExtendedCharacterCasing.Upper)> _
Public Shadows Property CharacterCasing() As ExtendedCharacterCasing
Get
'Return _casingSelected
Return MyBase.CharacterCasing = _casingSelected
End Get
Set(ByVal Value As ExtendedCharacterCasing)
_casingSelected = Value

If _casingSelected = ExtendedCharacterCasing.Lower Or _casingSelected = ExtendedCharacterCasing.Normal Or _casingSelected = ExtendedCharacterCasing.Upper Then
MyBase.CharacterCasing = _casingSelected
Else
'MyBase.CharacterCasing = Windows.Forms.CharacterCasing.Normal
MyBase.Text = StrConv(MyBase.Text, VbStrConv.ProperCase)

 MyBase.Update()

 End If

 End Set
 End Property

 Protected Overrides Sub OnKeyDown(ByVal e As System.Windows.Forms.KeyEventArgs)
 If _casingSelected = ExtendedCharacterCasing.Proper Then
 Me.Text = StrConv(Me.Text, VbStrConv.ProperCase)
 Me.Update()
 End If
 End Sub

 Public Overrides Property Text() As String
 Get
 If _casingSelected = ExtendedCharacterCasing.Proper Then
 'Return StrConv(MyBase.Text, VbStrConv.ProperCase)
 Return MyBase.Text = StrConv(MyBase.Text, VbStrConv.ProperCase)
 Else
 Return MyBase.Text
 End If
 End Get
 Set(ByVal Value As String)
 MyBase.Text = Value

 End Set
 End Property

End Class