I cannot get SyncBack to run under another users account, e.g. Administrator, when using the Scheduler. Why?
Profiles are by default user-specific, as they are stored in user-specific locations by user-name (for security reasons). The location SyncBack will look in for profiles when the Scheduler calls it is dictated by which user is running SyncBack, so if you change the credentials in a Scheduled Task, the Task will run as 'him', as will SyncBack, and SyncBack will thus look in 'his' location for the named profile instead, which may not exist there.
In SyncBackPro/SE* you can share profiles between all users if the profile is stored in the same folder as SyncBack itself. The users must have write access to the folder SyncBack is installed in, typically a folder in Program Files. On Windows Vista and newer, a regular user will not have write access to the installation folder.
SyncBack V8 (or newer) introduced the ability to store your profiles settings in a path you choose.
See this article for more details how to do this, and also to change the logging settings (highly recommended).
* SyncBackFree does not support shared profile storage in the program folder