>I believe I use Windows authentication (Trusted_Connection=Yes] in SQLStringConnect.)
>I don't understand the question on default database for login. In my SQLStringConnect there is a name of the database I am trying to connect; is that what it is?

The default database is specified for a login in SQL Server and used when none is provided during a login. When you specify database name in the connection string, the default DB has no relevance.

Are you using multiple Windows users on your computer?