For how to fix this see the toolbar keeps resetting article.

This did not solve the problem. What solved the problem iwas to disable all add-ons and add them back one at a time. I found that the last add-on I installed, Babylon, was causing the problem. I suggest that if you are having a problem similar to the one listed here, the first thing you should do is disable all add-ons using safe mode and see if the problem goes away. Then enable one add-on at a time using Tools and see which one is causing the problem. Only enable the add-ons you know you will use. Leave all others disabled or uninstall them. Some add-ons will cause problems.