Description: This error happens when a PHP file has a fatal error and is causing the site to crash. It could be related to malware or just a programing error. Either way, it should be fixed because the site is down.
Error example:
Fatal error: fatal flex scanner internal error--end of buffer missed in public_html/index.php on line 78
Clean up: It needs to be verified what is causing the error (hacked or hosting error). Contact support for help at support@sucuri.net.