This error indicates that there is insufficient free disk space available on the system for the backup to complete.
To complete the backup process, Online Backup requires a minimum free "Swap Space" equal to the size of the backup plus 60 MB. . For example, if the Online Backup account is a 1 GB account, you will need 1 GB + 60 MB free disk space on the PC to perform the backup.
The Online Backup program creates encrypted archives on the PC before it transmits the data to the backup servers. . These files are cleared once the backup completes. . When restoring online backups, the same process applies, but in reverse. . Online Backup uses the space to download the encrypted files and then decompresses them.