In rare circumstances it has been observed that SWG stopped updating antivirus definitions although new definitions were available on Symantec website.
Corruption of jlucache.xml file prevents AV defs updates from working
Symantec is aware of this issue and will update this document when a solution becomes available. Please subscribe to this article to be notified of any updates.
There might be a manual workaround available, please contact support for details.