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]] and [[Firewalls]] and http://kb.mozillazine.org/Firewalls See also http://kb.mozillazine.org/Browser_will_not_start_up ---- Not related to your question, but your above posted system details show outdated plugin(s) with known security and stability risks. *Shockwave Flash 10.0 r45 Update the [[Managing the Flash plugin|Flash]] plugin to the latest version. *http://www.adobe.com/software/flash/about/