Do a clean reinstall and download a fresh Firefox copy from http://www.mozilla.com/firefox/all.html and save the file to the desktop.
Uninstall your current Firefox version and remove the Firefox program folder before installing that copy of the Firefox installer.
It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.

You can skip the step to create a new profile, that is not necessary for this issue.

See http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

This is the same suggestion that was in the other two related posts. As I said in my original post, I read the other two similar posts and tried that suggestion.

It didn't work.

As I said, I went even further than the suggestion and uninstalled/deleted/cleaned out any file or folder that had either "Firefox" and "Mozilla" in it's name, as well as doing the same inside the Windows Registry. I checked and deleted even hidden folders.

I solved the problem.

The cause of the problem was Zone Alarm. I used the Firewall writeup in the Mozilla Troubleshooting document and renamed firefox.exe to firefox1.exe. I was able to launch Firefox. I then deleted all entries in ZoneAlarm relating to Firefox, then totally shutdown ZoneAlarm. I renamed the exe back to firefox, launched Firefox and it started. I re-enabled ZoneAlarm and Firefox still works.