membership problem

hi
i have problem runining my web site i have change the aspnetdb.mdf to another name and i change the connection string every thing work fine until i try to use the membership like this:
If User.Identity.IsAuthenticated Then
                If Roles.IsUserInRole("User") = True Then
the server will popup message telling me to login if not error page will appear?
the web host compny tell that you have this error:
3:34:01 PM w3wp.exe:7888 QUERY INFORMATION D:\hshome\c301695\alkobara.com\App_Data\ASPNETDB.MDF PATH NOT FOUND Attributes: Error
3:34:01 PM w3wp.exe:7888 QUERY INFORMATION D:\hshome\c301695\alkobara.com\App_Data\ASPNETDB.MDF PATH NOT FOUND Attributes: Error
3:34:01 PM w3wp.exe:7888 QUERY INFORMATION D:\hshome\c301695\alkobara.com\App_Data NOT FOUND Attributes: Error
3:34:01 PM w3wp.exe:7888 QUERY INFORMATION D:\hshome\c301695\alkobara.c ...