//
   lockPref("extensions.shownSelectionUI", true);
   lockPref("extensions.autoDisableScopes", 11);

   pref("general.config.obscure_value", 0);
   pref("general.config.filename", "mozilla.cfg");

I am having issues getting lockPref working on my Mac. I have followed instructions here, as well as looking in other places for solutions. I have created a mozilla.cfg file, as well as a local-settings.js file in /Applications/Firefox/Contents/Resources/defaults/pref, as follows: mozilla.cfg // lockPref("extensions.shownSelectionUI", true); lockPref("extensions.autoDisableScopes", 11); local-settings.js pref("general.config.obscure_value", 0); pref("general.config.filename", "mozilla.cfg"); These are both saved using Windows Latin encoding (have tried Windows Roman too). When opening Firefox, I am getting an error dialogue saying, "Failed to read the configuration file. Please contact your system administrator". I'm not sure where to go from here, as other solutions have involved UTF encoding problems and incorrect configuration values - I saved an empty mozilla.cfg file to attempt to rule that out, and the problem still persists. I have even substituted with files downloaded from GitHub, as they should have the correct encoding - no juice. FYI I'm using OS X 10.11.5 and Firefox 42.0. Thanks.