Sharepoint 2010 - Asp.net Password Recovery Control - Your attempt to retrieve your password was not successful. Please try again.

Hi everyone

I have created a recovery password page using ASP.net 2010 with PasswordRecovery Control, when i tried to retrieve my password it always says "Your attempt to retrieve your password was not successful. Please try again.", i don't know what is the cause, here's my code for the passwordrecovery page.

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
    <style type="text/css">

    .style14
    {
        width: 600px;
        height: 300px;
    }
    </style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
    <p>
        <img alt="" class="style14" src="log-in-image.gif" /></p>
</asp:Content>
<asp:Content ID="Content3" ContentPlaceHolderID="ContentPlaceHolder2" runat="server">
    <asp:PasswordRecovery ID="PasswordRecovery1" runat="server" 
        MembershipProvider="MyMembershipProvider">
    </asp:PasswordRecovery>
</asp:Content>
<asp:Content ID="Content4" ContentPlaceHolderID="ContentPlaceHolder3" runat="server">
</asp:Content>

on my webconfig, i set the enablePasswordReset and enablePasswordRetrieval into "true", and password format is "Encrypted".

I hope someone can help me on this, thanks and regards.