CalendarExtender não funciona ie8

O html está assim:   <asp:ScriptManager ID="ScriptManager1" runat="server" ScriptMode="Release" EnableScriptGlobalization="true"  EnableScriptLocalization="true" />
          
<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
                <ContentTemplate>
 <asp:panel id="pnl_movimento" runat="server" Width="714px" Visible="False">
                 
                    <table ID="tbl_dados" border="0" cellpadding="0" cellspacing="0" width="714">
                                    <tr>
<td valign="top" >
                                            <asp:Label ID="lbl_Data" runat="server" CssClass="bar_title">Data</asp:Label>
                                            <asp:RequiredFieldValidator ID="vld_DataSaida" runat="server"
                                                ControlToValidate="txt_DataSaida" Display="None" ErrorMessage="Informe a data"
                                                ValidationGroup="cab">*</asp:RequiredFieldValidator>
                                            <br />
                                            <asp:TextBox ID="txt_DataSaida" runat="server" AutoPostBack="True"
                                                contentEditable="false" Width="72px"
                                                ontextchanged="txt_DataSaida_TextChanged"></asp:TextBox>
                                            <asp:ImageButton ID="ibt_calendario" runat="server" Height="16px"
                                                ImageUrl="~/m_oper/images/Calendario.jpg"
                                                PostBackUrl="~/pasta/fichas.aspx" style="width: 16px;"
                                                Width="16px" />
                                            <br />
                                            <asp:Label ID="vld_data" runat="server" CssClass="alerta" Visible="False"
                                                Width="262px">Data não pode ser maior que data atual</asp:Label>
                                        </td>

Acredito que você não possa utilizar o CalendarExtender com o updatepanel do ajax.. Ele não oferece suporte.