AJAX :: Modal Popup And Background Page Not Grayed Out?

using .net 4.0 and trying to open a modalpopup with grid loading; it pops up but doesn't grayout the rest of the page, allowing more clicking on the grid. I want the page to grayout with modalpopup and disable any further activity until the grid is loaded.

[Code]....

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<script type="text/javascript" language="javascript">
var ModalProgress = '<%= ModalProgress.ClientID %>';
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(beginReq);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endReq);
function beginReq(sender, args) {
// shows the Popup
$find(ModalProgress).show();
}
function endReq(sender, args) {
// shows the Popup
$find(ModalProgress).hide();
}
function CallPrint(url, window) {
window.open(url, window, 'left=0,top=0,width=900,height=600,toolbar=1,scrollbars=1,status=0');
}
</script>
<div>
<asp:ModalPopupExtender ID="ModalProgress" runat="server" BackgroundCssClass="modalBackground" PopupControlID="panelUpdateProgress"
TargetControlID="panelUpdateProgress">
</asp:ModalPopupExtender>
</div>
<div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<table class="style1">
<tr>
<td>
<asp:Literal ID="litMedResult" runat="server"></asp:Literal>
</td>
</tr>
<tr>
<td>
<asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="1">
<asp:TabPanel ID="tpFilter" runat="server" HeaderText="Show AICE Filtered Meds">
<ContentTemplate>
<asp:GridView ID="gvFilteredMeds" runat="server" AutoGenerateColumns="False"
BackColor="White" BorderColor="#999999" BorderStyle="None" BorderWidth="1px"
CellPadding="3" GridLines="Vertical"
onrowdeleting="gvFilteredMeds_RowDeleting" DataKeyNames="AICEMedID">
<AlternatingRowStyle BackColor="Gainsboro" />
<Columns>
<asp:BoundField DataField="AICEMedID" Visible="False" />
<asp:BoundField DataField="node_descrp" HeaderText="Med" />
<asp:CommandField DeleteText="Remove From Filter"
HeaderText="Remove From Filter" ShowDeleteButton="True" >
<ControlStyle ForeColor="Red" />
</asp:CommandField>
</Columns>
<FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
<HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
<RowStyle BackColor="#EEEEEE" ForeColor="Black" />
<SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
<SortedAscendingCellStyle BackColor="#F1F1F1" />
<SortedAscendingHeaderStyle BackColor="#0000A9" />
<SortedDescendingCellStyle BackColor="#CAC9C9" />
<SortedDescendingHeaderStyle BackColor="#000065" />
</asp:GridView>
</ContentTemplate>
</asp:TabPanel>
<asp:TabPanel ID="tpAllMeds" runat="server" HeaderText="Show All Meds">
<ContentTemplate>
<asp:GridView ID="gvAllMed" runat="server" AutoGenerateColumns="False"
BackColor="White" BorderColor="#999999" BorderStyle="None" BorderWidth="1px"
CellPadding="3" GridLines="Vertical" DataKeyNames="node_id"
onrowdatabound="gvAllMed_RowDataBound">
<AlternatingRowStyle BackColor="Gainsboro" />
<Columns>
<asp:BoundField DataField="node_id" Visible="False" />
<asp:BoundField DataField="node_descrp" HeaderText="Meds" />
<asp:TemplateField HeaderText="Add to Filter List">
<ItemTemplate>
<asp:Button ID="btnAddMed" runat="server" Font-Bold="true" OnClick="btnAddMed_Click" Text="Add Med" />
</ItemTemplate>
<ControlStyle Width="100px" />
<HeaderStyle Width="60px" />
</asp:TemplateField>
</Columns>
<FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
<HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
<PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
<RowStyle BackColor="#EEEEEE" ForeColor="Black" />
<SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
<SortedAscendingCellStyle BackColor="#F1F1F1" />
<SortedAscendingHeaderStyle BackColor="#0000A9" />
<SortedDescendingCellStyle BackColor="#CAC9C9" />
<SortedDescendingHeaderStyle BackColor="#000065" />
</asp:GridView>
</ContentTemplate>
</asp:TabPanel>
</asp:TabContainer>
</td>
</tr>
<tr>
<td>
</td>
</tr>
</table>
</ContentTemplate>
</asp:UpdatePanel></div>
<div>
<asp:Panel ID="panelUpdateProgress" runat="server" CssClass="updateProgress" >
<asp:UpdateProgress ID="UpdateProg1" DisplayAfter="0" runat="server">
<ProgressTemplate>
<div style="position: relative; top: 45%; text-align: center;">
<img alt="Processing" class="style3"
src="Images/loading.gif" />Processing ...
</div>
</ProgressTemplate>
</asp:UpdateProgress>
</asp:Panel>
</div>
</asp:Content>