Jeffe, faça isto:
<cc1:ToolkitScriptManager ID="toolkitSM1" runat="server"/>
TextBox
<asp:TextBox ID="cpfConsuTextBox" runat="server" ></asp:TextBox>
MaskedEditExtender
<asp:MaskedEditExtender ID="cpfConsuTextBox_MaskedEditExtender" runat="server"
Mask="9999-9999" TargetControlID="cpfConsuTextBox">
</asp:MaskedEditExtender>