Sp_addlogin, Sp_adduser - Error 21770

I am trying to add a new user (SQL Server 6.5) from an application program (Delphi 4.0). I was hoping I could do this in a stored procedure that basically acts a a wrapper around the SQL Server stored procedures.

It partially works - here is my procedure:

create procedure AddUserToSQLServer(@loginame varchar(30),
@Password varchar(30) ) as
begin

-- Add User to SQL Server Database
exec mydb.dbo.sp_addlogin @loginame,@Password,'mydb'

exec mydb.dbo.sp_adduser @loginame

end

The sp_addlogin adds the login and sets the default database as mydb. This is OK, except the user still can not login to the application. So I added the sp_adduser. This gives the user access to the application, but I still have a problem. When I go into Executive Manager, and go to the Manage Logins screen by double-clicking on the newly added user, I get the message "Error 21770: The name 'loginame' was not found in the users collection" where loginame is the users login. I click OK to this message, and the user is displayed on the manage logins screen. Their default database is mydb, a check is in the Permit box and their username is in the User column. Alias and Group are blank. When I try to drop the user, I get the same error again (2 times), then error "Error 15175: [SQL Server] login 'loginame' is aliased or mapped to a user in one or more database(s), drop user or alias before dropping login".

The only thing I found that works is to go to SQL and issue sp_dropuser loginame, then I can drop the user.

Anybody see what's wrong? Or know of a FAQ that addresses this situation?

Thanks

Wayne