• get fresh installer of Firefox 8 from getfirefox.com
• remove current version fully, (Remove Program Files/Mozilla Firefox folder also)
• run clean install and try

Unfortunately, that didn't work. I uninstalled all versions of Firefox, and deleted the Mozilla / Firefox program folders. Then I tried to install the newest Firefox version with no success. Here's what happens: 1. The install completes succesfully. 2. When I go to start firefox, I get an hourglass for a few seconds, and then nothing.

When I start firefox with the Task Manager running, I can see Firefox.exe running for a few seconds between 39-50% CPU. But, then that stops after a few seconds.

Something else that is interesting: I can force firefox 8 to run when I click on a hyperlink from MS Excel. I just can't run it from the start menu, desktop, or taskbar. After I start Firefox with the hyperlink, I am successfully able to start a new session (not tab) from the taskbar.

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 and the updater 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