During the morning of May 10 (and again this evening), I left my computer running while I went to work.
When I returned, the systray icon had changed to a red warning "X" on it. (There was no "Your Antivirus is turned off" slide-out warning displayed, only an "X" on the systray icon.)
So, I tried using Norton Autofix, which did not return the systray icon to a "Secure" green status.
This may be a bug which needs to be fixed: Autofix should change the red warning "X" icon to "Secure" green status. (Because after all, the Autofix status reads, "Scan Complete, No Issues.")
Also, this may have something to do with LiveUpdate changing definitions (or whatever), or it may not. I can't tell. All I can say for sure is, is it's not always changing the icon back to "Secure" green status--sometimes it just leaves the "X" icon.
Please refer to this screenshot. Thanks.