Well, there could be many things that are going on. First, you need to make sure that you do in fact have the users deployed on the system. Bring up SQL Server Management Studio and ensure that your users are there. Second, make sure that the security key within your appliction lines up with the security key when the users were created. Otherwise, when you open the SecurityDialog within your application, you will see the user, but it will indicate that the user is invalid. These would be the first two things that I would check.If this doesn't get you going, please post the error or messages that you are receiving. Thanks.