adding members problem

Hi
I've wrote a webapplication using membership and all kind of the authentication and authorization stuff.
The users are stored on a remote SQL server (I don't use a local SQLEXPRESS database). So a defined in my webconfig a custom membership and a custom sqlRoleProvider. With a CreateUserWizard control I can add users to my application. So far no problem; I can add users and I find them stored in my SQL-database and for every new user I receive an email with a confirmation.
Now it comes: when I start the ASP.NET Web Site Administration Tool in VS 2008, under the security tab I've been told that there are 0 (!) Existing users. And yes, I selected under the provider tab my custom membership and roleprovider.
Then I tried to recall all users in a gridview. I used the following code:
<asp:GridView ID="GridView1" runat="server" DataSourceID="Ob ...