AJAX CollapsiblePanel control help needed?

I am using an AJAX CollapsiblePanel control but there are some problems?

Basically, the panel hides when i click the arrows but doesnt open when I click the arrows again - why is it doing that?

<%@ Page Title="Home Page" Language="VB" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="Default.aspx.vb" Inherits="AJAX_Panels._Default" %>

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

<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
<br />
<asp:Panel ID="pnlHeader" runat="server" Width="300px">
Product Information
<asp:Image ID="imgToggle" runat="server" ImageUrl="~/collapse.jpg" />
</asp:Panel>
<asp:Panel ID="pnlInfo" runat="server" Width="300px" BackColor="#66FFFF">
This panel will expand and collapse to show and hide text depending on user.
</asp:Panel>
<asp:CollapsiblePanelExtender ID="pnlInfo_CollapsiblePanelExtender" runat="server" Enabled="True" TargetControlID="pnlInfo" CollapseControlID="pnlHeader" ExpandControlID="pnlHeader" CollapsedImage="~/expand.jpg" ExpandedImage="~/collapse.jpg" ImageControlID="imgToggle" SuppressPostBack="True">
</asp:CollapsiblePanelExtender>
<br />

</asp:Content>