Firefox abruptly stopped working on my MacBook Air. When logged in as the admin, Firefox works fine. When a 2nd user logs into an account on the Mac, and tries to open Firefox, Firefox asks to install a helper tool. If I do so (with the admin credentials), the helper tool prompt goes away, but then if I click to open Firefox the icon just bounces and I get an "application not responding" warning. I have tried refreshing Firefox from the admin account. I deleted Firefox and deleted all user profiles, re-installed Firefox, and still the same thing happens (works fine on admin account, does not work for any other user on the Mac). I am also unable to open Firefox in troubleshoot mode (option key). Even with the option key the Firefox icon bounces on the dock and never opens. I can't share any data because I can't open the app. Any help would be appreciated. Thanks.