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

Your firewall may be blocking the access.

Remove all rules for Firefox 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.com/kb/Server+not+found
• https://support.mozilla.com/kb/Firewalls

Hi,

Thanks for replying. I have the microsoft firewall and an ESET antivirus program. As far as I can see, the firewall is as you recommended i.e. firefox and its the other processes are not blocked and the problem is still occuring.