NT Backup sucks but sometimes you don't have any other choice. Here is a working command line that you can insert into a Scheduled Task. Make sure that the scheduled task runs as a user with at least "backup" authority, and has a password assigned to it. You cannot setup a scheduled task that runs as a user without a password. Do not use the Administrator account, because the password might get changed somewhere along the line, which will cause your backup to not run.
This command line assumes that you have gone through the NT Backup wizard and have created a job called "Daily Data Backup" while you were logged into the Administrator account.
C:\WINDOWS\system32\ntbackup.exe backup "@C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\Windows NT\NTBackup\data\Daily Data Backup.bks" /n "Media created 4/1/2005 at 1:44 PM" /d "Daily Backup" /v:yes /r:no /rs:no /hc:on /m normal /j "Daily Data Backup" /l:s /p "4mm DDS" /um