TIBCO iProcess Engine makes an assumption when it installs. It assumes that the database owner name and the schema name for that user will match. With a standard mixed-mode SQL Server 2005 install this would be fine - throw Windows Integrated Authentication (WIA) in the mix and it gets complicated. SQL2k5 creates a dbo user, linked to a domain account, and a dbo schema. TIBCO assumes the schema name will match what it resolves the dbowner to (domain/user). It doesn't allow you to override this. It doesn't take what SQL2k5 says is the default schema for the user. It makes an assumption. Which then results in a error during installation or the creation of a schema that can break enterprise standards. And it's just ugly.
Don't make assumptions in your installers.