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

See also:

• http://kb.mozillazine.org/Browser_will_not_start_up

@cor-el I have tried configuring my firewall as well. The only browser that will launch on my PC is IE (Without ad-ons)

Which security software (firewall, anti-virus) do you have?