I saw in your More system details that you have a Yahoo extension (disabled) Is the problem only during updates? How do you do the updates? Auto, manual . . . https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save '''Note:''' Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.