Windows Backup running from command line

Hi everyone

We run a scheduled task to call Windows Backup utlility, which backs up to a tape.  Sometimes (perhaps every other time), it fails.

If we are able to spot it happening, we see the utility stops and asks for confirmation the media is in place.  If we just leave it, it gives up after a bit and exits.  If we confirm with a mouse click the same thing seems to happen.  If we try again, sometimes it works (we see the utility mounting the media then rewinding the tape)... or sometimes the same error occurs.

It seems to do this at random, with new or used tapes.  It would seem logical that it's something to do with backups already on the tape.  I though the command line we were using told the utility to overwrite whatever is on the tape and just get on with it.  Here's the line:

C:\WINDOWS\system32\ntbackup.exe backup "@C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\Windows NT\NTBackup\data\filename.bks" /n "Name of backup" /d "Name of backup" /v:yes /r:no /rs:no /hc:off /m normal /j "BACKUP" /l:f /p "4mm DDS" /um

Is there something wrong there?

We have 5 tapes - Mon to Fri.  Each morning, that days tape is loaded and the previous one removed and taken off site.  The task runs at 2am, and carries out a complete backup every time, not an incremental one.

If anyone can advise how to make this more reliable, that'd be great!

Simon