You install an earlier version of Firefox. If.. you're having difficulties with your first install of Firefox. Did you really un-install everything and then used Mozilla's installation guide for the latest version. Here's my best suggestion, re-install everything and see what happens.

Your feline friend, Stephanie

Did you check your security software (firewall)?

A possible cause is security software (firewall) 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 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.

See:

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

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