Check for the presence of a mozilla.cfg file in the Firefox program folder to initialize some prefs. This also involves the presence of a .js (JScript) file, probably in "defaults\pref" folder, that specifies to process this mozilla.cfg file. If you have .js files apart from the channel-prefs.js file, that sets app.update.channel, in the defaults\pref folder then open this file in an editor like Notepad and please post its content.<br /> Also please post the content of the mozilla.cfg file. There shouldn't be a mozilla.fcg file present unless you've created it yourself to initialize some prefs. If you have this mozilla.cfg file then best is to do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox. *http://kb.mozillazine.org/Preferences_not_saved#Other_solutions