Just confirming, you checked for new updates for both the Firefox browser software AND updates to any add-ons and plug-ins you have installed? You'll find these under the Tools menu in FF.
To check add-on updates, click the selection. Once there, also click the Plug-In icon. At the bottom of that window is a button to click for checking for plugin updates.
Also check your Windows Firewall settings. Nortons and the Windows Firewall had conflict problems several years ago. If memory serves me correctly, the Windows Firewall has to be disabled/turned off.