Every once in a while, a giant antivirus company will make a huge mistake by flagging a very important file as a threat.
As far as I know, Kaspersky once detected explorer.exe as a virus and quarantined the file making the entire Windows desktop, system tray and start menu to disappear!
Many years ago, Norton too detected Flash Player as a trojan called PWSteal. Now, it is AVG’s turn to do that.
Three days ago AVG detected a critical legitimate Windows file user32.dll as a trojan horse Generic9.TBN.