When I want to open the Tor Browser, I get a pop up: "Could not load XPCOM!" ... which is usually a not-updated Firefox. Do I have to download a fresh Tor Browser every time I update Firefox? Or what is my problem? Thanks....
The Tor browser is its own standalone and has nothing to do with what you have installed on your computer. I would redownload the zip file, extract it to a folder somewhere (your desktop perhaps) and run it directly from there. If you continue to get this error and Tor refused to load, you have something blocking Tor (anti-virus for example).