Scheduled NTBackup jobs start then immediately exit.

[jasonb]

This is because scheduled jobs will never overwrite used tapes, despite anything you tell the program to do in the Wizard.

To fix this, edit the command line being used for the backup task in Start -> Settings -> Control Panel -> Schedule Tasks. At the end of the list of commands, add the following switch: /um

Now, NTBackup will use the tape in the drive even if it does contain data (so long as you've also told it to do so when defining the job via the Wizard).