Me too!

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your extensions and then try to find which is causing it by enabling one at a time until the problem reappears. You can use "Disable all add-ons" on the Safe mode start window. You have to close and restart Firefox after each change via "File > Exit" (on Mac: "Firefox > Quit")

I found another tip somewhere on this forum: (1) download the lastest version of Firefox, (2) rename your old Firefox directory in 'Program Files' into something else (like 'Mozilla Firefox Old') and (3) just reinstall Firefox. I did this two days ago. For me, so far so good, no scripts errors anymore.