- The other option is to also update Internet Explorer via Windows Update. (It is pretty important to make sure IE is up to date even if you don't use it due to security flaws with older versions.)

- It's a bit late but I will post this solution for everyone else who has script errors. I dont have the english IE so I have to translate it freely - go to the option menu of the IE -> then internetoptions -> tab "advanced" -> reset -> reset
It will tell you that the changes active after a restart - do NOT restart the pc!
just open the ff launcher and the script error should not bother you anymore.
You have to do this everytime after a restart of the pc, if you want a permanent solution i think you will need to reinstall windows.

this was testes on the IE version 11.

hope this will help at least some of you.