Check here

• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

Thanks for effort, but the problem is still here. Just to clarify here is the complete story: On Feb. 6 I upgrade from Firefox 18.0.1 to 18.0.2 and Firefox does not start any more. So after many trials I start using Chrome and everything was fine. After 3/4 days I tried to install again Firefox 18.0.2 and it start working as usual: only some trouble with PDF files. Today I have done the upgrade from 18.0.2 to 19.0 and again Firefox does not start. I had deleted Firefox from Norton Firewall list and than added again, but there is no solution. From Norton I get the message on updater (see below) and nothing happen.

I start again using Chrome, but it was a pity such problem after several years of Firefox usage.

RIccardo

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

Thanks cor-el, but no positive result. I re-install Firefox 19 and checked it, but I get similar effect: "updater.exe is safe..." and Firefox does not start. I tried also to de-activate SmartFirewall of Norton, but I simply don't get the message for updater.exe. Than I reboot in safe mode with network. Chrome work perfectely while Firefox does not start.

Reboot normally and check again: Updater.exe message and nothing happens.

Regards riccardo