You can make a one-time-backup from 2 different places in the iTSec plugin:
1. The most obvious, from the Backups tab or Backups menu option.
Simply clicking on the “Create Database Backup” button will start a one-time-backup.
My guess is that this is where you now get the “Security error!”.
2. From the “Important First Steps” popup screen. Go to the iTSec Dashboard menu option and then click at the top right of the screen on the “Show Intro” link. Then simply click on the “Make a backup” button from the popup screen.
The above assumes you are trying to make a one-time-backup and NOT a scheduled backup.
If you indeed get the “Security error!” using option 1, try option 2.
You probably wonder what’s the difference ?
The resulting backup is identical BUT option 1 starts a one-time-backup by submitting a FORM while option 2 starts a one-time-backup by using an AJAX request.
There is an extra check (which in your env results in the “Security error!”) done in the code of the FORM method compared to the code of the AJAX request method.
This is just a quick workaround to (hopefully) be able to make a one-time-backup.
This post does not answer why the extra check fails in the code of the FORM method (You seem to have other issues which might be related…)
dwinden