Scheduled backups

I cannot get scheduled incremental backups to function,
even after filling out the password screen, as suggested
by Sharon last week. Then I thought the problem might be
that I'd not given myself a password on the system. I did
so, but that did not help. I'm a single user on XP
Professional. I've created a folder in which I have a
couple of files. I first do a Normal backup. Then change
the files, and setup up an Incremental backup. If I do it
right away - it works. If I schedule it for later, it
doesn't. I note that in Backup Details of Scheduled Job
Options there is no mention of when the job should run,
although I don't if there should be such a mention, but
one item intrigues me:"Do not restrict access to owner or
administrator". I would have thought that the purpose of
making it password protected was to restrict access.
In the Backup Utility [Restore & Manage Media] window
there is a column headed "Removable Media" under
which "N/A" appears. I know what N/A means, but wonder if
that might be a clue as why I cannot get scheduled
incremental backups to work.
In the Backup Utility [Schedule Jobs] window, there is a
little green - it looks like a "1" or an "l" to the left
of the scheduled incremental job icon. I cannot find any
reference to it in the help material,so wonder what it
may mean.
Lastly, should I be getting an "Operation Failed" error
message when a scheduled backup is not realised?
Ian