JavaScript onchange事件未在IIS7中触发

Source Code:

<ajaxToolkit:TabContainer ID="tbMBQOutputs" runat="server" Width="100%" Height="720px">
    <ajaxToolkit:TabPanel ID="tbDashboard" runat="server" Height="100%" ToolTip="Dashboard">
    <HeaderTemplate>Dashboard</HeaderTemplate>
    <ContentTemplate>
        <asp:UpdatePanel ID="upDashboard" runat="server" UpdateMode="Conditional">
        <ContentTemplate>
           <table bgcolor="#E6E6FA" align="center" border="0" cellpadding="0" cellspacing="0" style="width: 100%; height: 99%; border: solid 1px black; margin-left: 1px; margin-right: 1px;">
           <tr>
               <td>
                    <asp:Panel ID="pnlDashboard_DC" runat="server" GroupingText="Dashboard">
                    <table align="center" border="0" cellpadding="0" cellspacing="0" style="width: 100%; height: 99%; border: solid 1px black; margin-left: 1px; margin-right: 1px;">
                    <tr>
                        <td align="center">
                             <asp:Label ID="lblReportCycle_DB" runat="server" Text="Report Cycle"></asp:Label>&emsp;   
                             <asp:DropDownList ID="ddlReportCycle_DB" runat="server" AutoPostBack="true" Width="140px" CssClass="tb2" OnSelectedIndexChanged="ddlReportCycle_DB_SelectedIndexChanged" ></asp:DropDownList>
                          </td>
                     </tr>                         
                     <tr>
                          <td align="center">
                               <asp:Label ID="lblMsgDashBoard_DB" runat="server" Font-Bold="true" ForeColor="Green"></asp:Label>
                          </td>
                      </tr>
                 </table>
                 </asp:Panel>
            </td>
            </tr>
            </table>
            </ContentTemplate>
       </asp:UpdatePanel>
       </ContentTemplate>
       </ajaxToolkit:TabPanel>
   </ajaxToolkit:TabContainer>
<ajaxToolkit:TabContainer ID="tb