Validation controls inside of UpdatePanel doesn't work

I had a RegularExpressionValidator inside the update panel which not working it dosen't show the error message if i remove updatepanel it works can any one helps me to work the RegularExpressionValidator inside the updatepanel 

<asp:Panel ID="pnlPopup"  BorderStyle="Solid" runat="server" >
   <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
   <ContentTemplate>

       <div style="background-color:GrayText;">
           <table border="0">
               <tr>
                   <td colspan="3" style="background-color:Maroon;color:White;font-weight:bold" > Time Sheet Entry </td>
               </tr>
               <tr>
                   <td><asp:Label ID="lblEtyID" Text="EntryID" runat="server" Visible="False"></asp:Label></td>
                   <td><asp:TextBox ID="txtEtyID" runat="server" Enabled="False" Visible="False"
                           Width="400px"></asp:TextBox></td>

               </tr>
               <tr>
                   <td> <asp:Label ID="lbluserid" Text="UserID" runat="server" Visible="False"></asp:Label></td>
                    <td><asp:TextBox ID="txtUserID" runat="server" Enabled="False" Visible="False"
                            Width="402px"></asp:TextBox></td>
               </tr>
               <tr>
                   <td><asp:Label ID="lbltypeid" Text="Type" runat="server"></asp:Label></td>
                   <td><asp:DropDownList ID="ddlTypeid" runat="server" Width="408px" AutoPostBack="true"
                         DataTextField="ItemName" AppendDataBoundItems ="true"  onselectedindexchanged="ddlTypeid_SelectedIndexChanged">
                           <asp:listitem selected="True" text="--Select--" value=""></asp:listitem>
                           </asp:DropDownList> </td>
               </tr>
               <div id="divTypedevelopment"  runat="server">
               <tr>
                   <td><asp:Label ID="lblProID" Text="ProductName" runat="server"></asp:Label></td>
                   <td><asp:DropDownList ID="ddlproductid" runat="server" AutoPostBack="true"
                          AppendDataBoundItems ="true"  onselectedindexchanged="ddlproductid_SelectedIndexChanged" Width="406px">
                            <asp:listitem selected="True" text="--Select--" value=""></asp:listitem>
                          </asp:DropDownList></td>
                          <td><asp:Label ID="Label5" runat="server" Text="*" style="color:Red"></asp:Label></td>
               </tr>
               <tr>
                    <td><asp:Label ID="lblverid" Text="VersionNumber" runat="server"></asp:Label></td>
                    <td><asp:DropDownList ID="ddlversionid" runat="server" Width="408px">
                    <asp:listitem selected="True" text="--Select--" value=""></asp:listitem>
                    </asp:DropDownList></td>
                    <td><asp:Label ID="lblmand" runat="server" Text="*" style="color:Red"></asp:Label></td>
               </tr>
               <tr>
                    <td class="style2"><asp:Label ID="lblbug" Text="BugID" runat="server"></asp:Label></td>
                    <td class="style2"><asp:TextBox ID="txtBugid" runat="server" Width="30%"></asp:TextBox>
                    <asp:RequiredFieldValidator runat="server" ControlToValidate="txtBugid" ErrorMessage="RequiredFieldValidator"></asp:RequiredFieldValidator></td>
                    <td class="style2"><asp:Label ID="Label1" runat="server" Text="*" style="color:Red"></asp:Label>
                        <%--<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server"
                              ControlToValidate="txtBugid" ValidationGroup="First" ErrorMessage="Enter only Numbers" > </asp:RegularExpressionValidator>--%>
                    </td>
               </tr>
               </div>
                <div id="divTypesupport"  runat="server">
               <tr>
                     <td><asp:Label ID="lblsuppid" Text="SupportID" runat="server"></asp:Label></td>
                     <td><asp:TextBox ID="txtSupportid" runat="server"></asp:TextBox> </td>
                     <td><asp:Label ID="Label2" runat="server" Text="*" style="color:Red"></asp:Label>
                         <%--<asp:RegularExpressionValidator ID="RegularExpressionValidator2" runat="server"
                          ControlToValidate="txtSupportid"  ValidationGroup="First"  ErrorMessage="Enter only Numbers"></asp:RegularExpressionValidator>--%>
                     </td>
               </tr>
               </div>
                <div id="divTypedescription"  runat="server">
               <tr>
                     <td><asp:Label ID="lblDescription" Text="Description" runat="server"></asp:Label></td>
                     <td><asp:TextBox ID="txtDescription" runat="server"></asp:TextBox></td>
                     <td><asp:Label ID="Label3" runat="server" Text="*" style="color:Red"></asp:Label></td>
               </tr>
               </div>

               <tr>
                     <td><asp:Label ID="lbldate" Text="Date" runat="server"></asp:Label></td>
                     <td><asp:TextBox ID="txtDate" runat="server" Enabled="False"></asp:TextBox></td>

                     <td></td>
               </tr>
               <tr>
                     <td><asp:Label ID="lbleffort" Text="Effort" runat="server"></asp:Label></td>
                     <td><asp:TextBox ID="txtEffort" runat="server" Width="30%"></asp:TextBox>
                     <asp:RegularExpressionValidator ID="RegularExpressionValidator3" runat="server"
                           ControlToValidate="txtEffort" ValidationExpression="^[0-9]*$"  ErrorMessage="Enter only Numbers" EnableViewState=true> </asp:RegularExpressionValidator></td>
                     <td><%--<asp:Label ID="Label4" runat="server" Text="* in Hrs" style="color:Red"></asp:Label>--%>

                     </td>
               </tr>

               <tr >

                   <td ><asp:Button ID="btnSubmit" Text="SUBMIT" runat="server"
                           onclick="btnSubmit_Click" /></td>

                   <td> <asp:Button ID="btnCancel" Text="CANCEL" runat="server"
                           onclick="btnCancel_Click"  CausesValidation="false"/></td>
                           <td></td>

<%--<asp:ValidationSummary ID="ValidationSummary" ShowSummary="False" ValidationGroup="First" ShowMessageBox="True" runat="server" />--%>
               </tr>

               <tr>
                    <td colspan="2"><asp:Label ID="lblInsinfo" runat="server" ForeColor="#FF3300"></asp:Label> </td>
               </tr>
           </table>
         </div>
   </ContentTemplate>
   </asp:UpdatePanel>
             <%--<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1"
                   DisplayAfter="0" DynamicLayout="true">
                   <ProgressTemplate>
                       <div id="ProgressBar" class="ajax-loading">
                       Working on your request...</div>
                   </ProgressTemplate>
               </asp:UpdateProgress>--%>
   </asp:Panel>