Sorry, here is the correct code snippet:

<div style="overflow:scroll;height:85%;border:1px solid;" id="divGrid">
       <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" OnLoad="UpdatePanel1_OnLoad">
            <ContentTemplate>
                <asp:GridView ID="GridView1" runat="server"
                    AllowPaging="True" AllowSorting="True" SkinID="gridView" OnDataBound="GridView1_OnDataBound">
                    <Columns>
                        <asp:TemplateField HeaderText="Select">
                        <HeaderTemplate>
                            <asp:CheckBox ID="chkBoxHeader" runat="server" />
                         </HeaderTemplate>
                            <ItemTemplate>
                               <asp:CheckBox ID="chkBoxRow" runat="server" />
                            </ItemTemplate>
                        </asp:TemplateField>
                    </Columns>
                </asp:GridView>
                <asp:Literal  ID="CheckBoxIDsArray" runat="server" ></asp:Literal>
                <input type="hidden" id="hdnSelChkBoxIDs" name="hdnSelChkBoxIDs" value="<%=selectedHdnString %>"/>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="btnSearch" EventName="Click" />
            </Triggers>
        </asp:UpdatePanel>
    </div>


  <cc1:UpdatePanelAnimationExtender ID="upae" BehaviorID="animation" runat="server" TargetControlID="updatePanel1">
        <Animations>
            <OnUpdating>
                <Parallel duration="0">
                    <%-- place the update progress div over the gridview control --%>
                    <ScriptAction Script="onUpdating();" />
                    <FadeOut MinimumOpacity=".5" />
                 </Parallel>
            </OnUpdating>
            <OnUpdated>
                <Parallel duration="0">
                    <%--find the update progress div and place it over the gridview control--%>
                    <ScriptAction Script="onUpdated();" />
                    <FadeIn MinimumOpacity=".5" />
                </Parallel>
            </OnUpdated>
        </Animations>
    </cc1:UpdatePanelAnimationExtender>
    <div id="updateProgressDiv" style="display:none; position:absolute;">
        <span style="color:#fff; margin:3px">
            <asp:UpdateProgress ID="UpdateProgress2" runat="server">
                <ProgressTemplate>
                    <asp:Image ID="Image2" runat="server" ImageUrl="~/Images/loader.gif" />
                        Loading...
                </ProgressTemplate>
            </asp:UpdateProgress>
        </span>
    </div>