All my Firefox addons get re-enabled when I reboot

I have the Comcast version of Norton Internet Security.  Recently, I've started having the problem that every time I reboot my system, Firefox re-enables all the add-ons I have disabled, including the Norton toolbar, but also other things like the Skype extension.  These are things I don't want to clutter up Firefox with, but there is no way to uninstall them altogether so I have to keep disabling them after every reboot.  Past messages on this forum indicate that this is a problem caused by Norton's products.  I don't like any product messing with my system settings like that.  If I want to disable an add-on, it's my system not yours, so I should be able to do it and let it stick.