CalendarExtender not working

hi

i'm using CalendarExtender but calendar is not shown at all when i click on textbox or image button, so i must be doing something wrong and can't figure it out.

i'm using VS2008, framework 3.5.

this is my code:

<%@ Page Title="" Language="VB" MasterPageFile="~/PlanMaster.master" AutoEventWireup="false" CodeFile="PlanTrip.aspx.vb" Inherits="PlanTrip" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <style type="text/css">
        .divRectangle
            {
                width:572px;
                height:590px;
                border: solid 1px #6B696B;
                padding-left:5px;
                padding-top:5px;
                padding-bottom:5px;
                position:relative;
                /*position:absolute;*/
                margin: auto;
                top: 0; left: 0; bottom: 0; right: 0;
            }
            
        .pnl
        {
            width:580px;
            height:604px;
            background-color:#F7F7DE;
        }

.divBlank20
{
    height:20px;
}

.lbl
{
    width:150px;
}

.txt
{
    width:140px;
}
    </style>
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="Main" Runat="Server">
    <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering ="true">
    </asp:ScriptManager>
    <div class="divHeading">
        <h2>
            <asp:Label ID="lblHeading" runat="server" Text="Plan trip"></asp:Label>
        </h2>
    </div>
    <div class="divBlank20"></div>
    
    <%--<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
        <ContentTemplate>--%>
            <div>
                <asp:Label ID="lblError" runat="server" Text=""></asp:Label>
            </div>
            <asp:Panel ID="pnlNew" runat="server" CssClass="pnl">
            <div class="divRectangle">
                <div>
                    <asp:Label CssClass="lbl" ID="Label7" runat="server" Text="Date from:"></asp:Label>
                    <asp:TextBox CssClass="txt" ID="txtDateFrom" runat="server"></asp:TextBox>
                    <cc1:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="txtDateFrom" ></cc1:CalendarExtender>
                    <%--<asp:ImageButton ID="btn" runat="server" ImageUrl="images/Calendar_scheduleHS.png" />--%>
                    <%--<cc1:CalendarExtender ID="CalendarExtender1" runat="server" TargetControlID="txtDateFrom" PopupButtonID="btn"></cc1:CalendarExtender>--%>
                </div>

                <div class="divBlank20"></div>
                <div style="float:left; width:100px;">
                    <asp:Button ID="btnCancel" runat="server" Text="Cancel" />
                </div>
                <div style="float:left; width:460px; text-align:right;">
                    <asp:Button ID="btnSave" runat="server" Text="Save" />
                </div>
            </div>
            <div class="clear"></div>
            </asp:Panel>
            <div class="divBlank20"></div>
       <%-- </ContentTemplate>
    </asp:UpdatePanel>--%>
</asp:Content>

i have to say that i can't use popupmodal extender (doesn't popup) as well ...

thanks for help in advance