Hi,
I've just figured out that scheduled scans don't happen unless you are logged in. If you are logged out at the time the scheduled scan is due (i.e. the computer is at the Windows Vista login screen waiting for a user to click on their username/icon), then:
1. the scheduled scan is never performed
2. when a user next logs in, the scan is not performed then either
3. the "next scan due" date is silently changed according to the schedule
So, if, like me, you have a scan scheduled every three days at 2am, and you always log out at night but leave your computer switched on, then the scan never happens but the scheduler happily and silently keeps advancing the next scan date by three days without ever actually performing the scan.
Is this behaviour documented anywhere?