That error appears to come from an add-on. To test this try the procedure in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article.

When you check your list of add-ons, look for an add-on that has "saff" in its name or the initials s.a.f.f. , that will likely be the one causing the problem.

I uninstalled and then reinstalled.Cleared all the setting during uninstallation. Still get the same problem.

saffplg.js is part of McAffee Site Advisor simply uninstalling this software helped, possible there is less invasive way

What does McAfee have to say about the bad behavior of saffplg.js ??