AlwaysVisible? where is it because I can't see it?

Hi

I'm using the always visible control and I face a problem. Please access to:

http://cheirabem.com/mostraperfumes00.aspx?marca=Burberry&sexo=Masculino

And You well see the control alwaysvisible is not always visible . The code is easy to implement but you can see the control hides and the buttons on it sometimes are not enabled. The pictures are on a listView

<!-- allways on top controlo aqui --><asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager><ajaxToolkit:AlwaysVisibleControlExtender ID="AlwaysVisibleControlExtender1" runat="server" TargetControlID="Panel2" UseAnimation="False" HorizontalSide="Right" /><asp:Panel ID="Panel2" runat="server" CssClass="pnlBackGround"><h2>Filtrar</h2><asp:Button ID="btnHomem" runat="server" Text="Masculino" OnClick="mostra_Homem" /><asp:Button ID="btmMulher" runat="server" Text="Feminino" OnClick="mostra_Mulher" /></asp:Panel><!-- fim do allways on top controlo -->

Thank you