FF upgrades have not always been kind.
I have used FF since about version 0.7. Some upgrades caused havoc with FF and some created other problems on my computer.
After version 2.0.0.11 (IIRC) messed up a bunch of extensions, and I finally got that cleaned up by deleting and installing an older version, I turned off the automatic upgrade feature.
You might try uninstalling and reinstalling FF. [I am still running 3.0. I didn’t upgrade to 3.1 — I cringe every time I see new verion or ‘upgrade’.]
Will try uninstalling & reinstalling, thanks... didn’t even cross my mind, lol