In the about:config the entry is called datareporting.healthreport.service.enabled

Does this entry change as well when you try to restart Firefox and have already disabled it?

There is software like Advanced SystemCare with its Surfing Protection feature that can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved

srothman99 said

I deselect Enable FIrefox Health Report but when I restart the browser it is renabled. I'm using version 39.0. Is there a registry setting or preferences file I can manually update?

I reset to default preferences and then everything was fine. I guess the prefs file was corrupted.