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>