Thanks Kim. I really appreciate the assistance.
For the record, the "mygeodatabase_owner" user definitely had "db_owner" permissions assigned, and was set to use "dbo" as it's default schema, but for some reason that setup doesn't work. For my purposes it really doesn't matter what schema is used, as long as I can get the shapefile imported into the DB.
As far as the "Ideas" page, my one suggestion would be for any tool that creates a geodatabase, such as the ArcSDE post-install tool, to set up everything that is required for a GDB, including a schema with the same name as the user, since that seems to be necessary.
Thanks again 🙂
Regards,
Dave