At times the following message could show up in the Messages window or during use of the DB Load utility:
U0003592 Status: '42000' Native error: '15517' Msg: 'Cannot execute as the database principal because the principal "dbo" does not exist, this type of principal cannot be impersonated, or you do not have permission.
The user specified (in this case "dbo") is not in the connect string, but is actually the database owner. The customer does not expect any user other than the logged-in database user to be accessed.
This usually happens on a reproduced or mirrored database. What happens is that the DB Load runs the chngdb.sql file. The end of this creates a stored procedure that uses "EXECUTE AS SELF" statement:
CREATE PROCEDURE UC_Truncate_Table
CREATE PROCEDURE UC_Update_Stat_Table
More information can be found here: http://support.microsoft.com/kb/913423
A look at the stored procedure within your database will show that Automic is pulling the DB owner rather than the logged-in user to run this procedure.