SharePoint - asp:ChangePassword control

While using the asp:ChangePassword control within a SharePoint application page I was getting the following exception.

Exception of type 'System.ArgumentException' was thrown.Parameter name: encodedValue

Using Fiddler I tracked this error down to the .ASPXAUTH cookie.   Setting this cookie back to null fixed this issue for me.

1. Call code behind method onChangedPassword

<asp:ChangePassword ID="cpUser" MembershipProvider="MembershipProviderName" OnChangedPassword="cpUser_PasswordChanged" DisplayUserName="true" runat="server"> </asp:ChangePassword>

    2.  Clear .ASPXAUTH cookie

protected void cpUser_PasswordChanged(object sender, EventArgs e){ if (Request.Cookies[".ASPXAUTH"] != null) { HttpCookie myCookie = new HttpCookie(".ASPXAUTH"); myCookie.Expires = DateTime.Now.AddDays(-1d); myCookie.Path = ApplicationName(); Response.Cookies.Add(myCookie); } }