• LiveUpdate sessions end with a LU1866 error stating there is insufficient disk space to continue
• The system appears to have sufficient disk space

The following errors may be present in the log.liveupdate:

• Unable to retrieve content length header for file being downloaded from server; err=12150; desc=The requested header was not found
• ERROR: Insufficient free disk space is available to continue downloading the file
  

This return code is primarily generated in environments with Proxy servers or firewalls that strip content length header information from HTTP or FTP communications. Other possible causes are:

• Proxy servers or firewalls that compress or encrypt file header information
• Other 3rd party applications that filter Internet traffic (ie AntiVirus, or content filtering appliances)
• Low disk space on the System drive

As this issue can have more than one cause, it may be necessary to try any/all of the solutions below to resolve this issue:

1. Confirm there is sufficient free space and no disk usage quotas preventing LiveUpdate from writing to it's temporary Downloads folder on the %SYSTEMDRIVE% (Note: LiveUpdate can be installed to any arbitrary drive location on the system, but the Downloads directory is always located on the %SYSTEMDRIVE%).

It may be necessary to free disk space by deleting the contents of the LiveUpdate Downloads folder at:

• %SYSTEMDRIVE%\ProgramData\Symantec\LiveUpdate\Downloads on Windows Vista and above
• %SYSTEMDRIVE%\Documents and Settings\All Users\Application Data\Symantec\LiveUpdate\Downloads on Windows XP

2. Ensure any proxy, firewall or content filtering applications or devices are not stripping header information from FTP or HTTP traffic - especially file size header information

3. Ensure any proxy, firewall or content filtering applications or devices are configured not to filter/scan LiveUpdate traffic from the following locations:

• liveupdate.symatnecliveupdate.com over HTTP
• liveupdate.symantec.com over HTTP
• update.symantec.com over FTP

4. Ensure any network-based antivirus scanners are configured to exclude LiveUpdate content from scans

If the issue persist check resolution of KB: 

https://knowledge.broadcom.com/external/article/226873/failed-to-execute-schedule-due-to-insuff.html