I suspect you ought to be disabling or uninstalling Norton software not downgrading Firefox to an unsfe and insecure old version. Please list exactly what security related software you are using, with full names, and version numbers. Please include the details of any related bundled software for backups or toolbar use. Security related software often includes a core component, the Anti Virus software, which usually continues to work as long as it is paid for and up to date. However the (often of speculative value) additional software ceases to work until it is updated to work with the new Firefox release. These optional extras may not be updated and made available immediately. Firefox 45 has only just come out. I know Trusteer Rapport software is causing issues. I am not yet certain about Norton's software. At least in my country Norton 360 seems to have been replaced with other products * See http://uk.norton.com/norton-security-with-backup?inid=hho_nortoncom_eoa_360_learn&lg=en&ct=GB I note you are using Windows 10. For ordinary domestic use that comes with built in security software including Anti Virus and a Firewall. Firefox itself has basic Phishing and Malware protection built in and turned on by default * [[How does built-in Phishing and Malware Protection work?]]