Zkuste řešení podle článku nápovědy [[Firefox nejde spustit]] v části [https://support.mozilla.org/cs/kb/Firefox%20nejde%20spustit#w_xulrunner-chyba XULRunner - Chyba].

Zkus to podle tohoto: '''XULRunner - Error''' If you see the message, "XULRunner - Error: Platform version <x.x.x.x> is not compatible with minVersion <x.x.x.x>"" ("<x.x.x.x>" depends on version number), after a software update, use another browser to download the Firefox installer from the [http://getfirefox.com/ Firefox download page], save it to the desktop or other location, delete the Firefox installation directory and then reinstall Firefox. If Firefox still does not start, see the [https://support.mozilla.org/en-US/kb/firefox-wont-start-find-solutions#w_firefox-will-not-start-after-updating Firefox will not start after updating] section below.