https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save Scan for malware as well. * Malwarebytes' Anti-Malware - http://www.malwarebytes.org/mbam.php * SuperAntispyware - http://www.superantispyware.com/ * Spybot Search & Destroy - http://www.safer-networking.org/en/index.html * AdAware - http://www.lavasoftusa.com/software/adaware/ If these don't find it or can't clear it, post in one of these forums for specialized malware removal help: * http://www.spywarewarrior.com/index.php * http://www.spywareinfoforum.com/ * http://bleepingcomputer.com/ * http://www.thespykiller.co.uk/index.php?board=3.0 * http://forums.whatthetech.com/index.php?showforum=27

If you do not keep changes after a restart then see: *http://kb.mozillazine.org/Preferences_not_saved