OK. Thanks Dave Y. for your input. I appreciated your efforts.
It has to be an old *.dll as it affects all versions of Firefox, young and old. I suspect that something happened while amalgamating all of my old dll folders to get YUM/RPM to work so that is where I'll look next.
And David G., with respect to trying Seamonkey, I will give it a try, but since all versions of Firefox is affected I cannot see how Seamonkey would be any different, but one never knows. Maybe there's a different dll requirement.
I think that I will just rename my remaining dll folders temporarily, copy across the dll folders from another machine, (that doesn't have this problem), and see what happens from there. I have no doubt that this will have serious consequences for my servers/services, but I will suffer that until I can narrow down what is causing this specific problem... it is very strange though, that nothing else is affected only Firefox.
Other than this this one issue I have everything working very smoothly now with many services updated/upgraded and this setup is very stable. Firefox is the last issue.
Then it will be time for backups... but I am not there yet.