Installed the new version of Firefox this a.m., and now have completely lost all internet access (including Explorer, as well as Firefox). Error message that Java Console wasn't compatible. Still able to send/receive e-mail using Thunderbird, so it is not a network issue. Since I cannot access internet after installing new version, it makes it tough to troubleshoot on-line. (Using a different computer on network to send this). HELP!

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

You can uninstall (remove) the Java Console extensions and disable the Java Quick Starter extension if you have that one as well, you do not need them to run Java applets.

See http://kb.mozillazine.org/Java#Multiple_Java_Console_extensions

http://www.java.com/en/download/help/quickstarter.xml - What is Java Quick Starter (JQS)? What is the benefit of running JQS? - 6.0

Disable the Java Quick Starter extension: Tools -> Addons -> Extensions
Control Panel -> Java -> Advanced tab -> Miscellaneous -> Java Quick Starter (disable)