Firefox has always been my default browser but starting a couple of days ago whenever I start Firefox following a system boot/reboot it asks me if I want it to be the default. If I click on yes it only retains the setting till the next system start then the question is asked again. If I say no and check in the options it claims it is not set as the default browser but if I check in Windows system setting default apps. it is shown as the default browser! I updated Firefox from ver. 42.0 to 43.0 but it made no difference.