Backup fails with "Fatal error writing backed up data" and the message "1 items and their content (4044525)

This article describes a particular instance of  the error "Fatal error writing backed up data" while Netvault is trying to backup /etc/mnttab.

Backup fails with following error messages:

Severe Error 2008/01/24 02:12:21 113 Data Plugin sdc_ihousing Fatal error writing backed up data
Severe Error 2008/01/24 02:12:22 113 Data Plugin sdc_ihousing Fatal error processing children of 'etc'
Severe Error 2008/01/24 02:12:22 113 Data Plugin sdc_ihousing Fatal error processing children of '/'
Warning 2008/01/24 02:12:22 113 Data Plugin sdc_ihousing Fatal error backing up selected item '/' or its children
Severe Error 2008/01/24 02:12:22 113 Data Plugin sdc_ihousing Failed while backing up items
Job Message 2008/01/24 02:12:22 113 Media SDC-BACKUP (SDC-BACKUP: f:\virtuallib\VirtualLibrary) Drive 'DRIVE 2:SDC-BACKUP' has completed its transfer
Warning 2008/01/24 02:15:46 113 Data Plugin sdc_ihousing 1 items and their contents could not be backed up
contains "/etc/mnttab : File has been truncated"