Did you check your security software (firewall)?

A possible cause is security software (firewall) that blocks or restricts Firefox without informing you about that, possibly after detecting changes (update) to the Firefox program.

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.

See Server Not Found - Troubleshoot connection problems and Configure firewalls so that Firefox can access the Internet and http://kb.mozillazine.org/Firewalls

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

The only firewall I have is the Windows firewall. I tried removing the exception for Firefox and then opening to gain permission but just had the same blank "untitled" page iin front of me. I went back and added Firefox to my exceptions list.