Try downloading Firefox from Mozilla, run firefox-bin from the folder and see if you have the same issue. https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

It works! but from now on, do I have to launch firefox always using firefox-bin within the folder? or is it possible to make a launcher with the logo as it was before?

I made shortcuts on the my desktop. Here are the options I get when dragging from the folder, I used the link here option. see screenshot

Thanks!