On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.If Firefox is not running, you can start Firefox in Safe Mode as follows: Click the menu button, click Help and select Restart with Add-ons Disabled.If Firefox is open, you can restart in Firefox Safe Mode from the Help menu: Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).
Try Firefox Safe Mode to see if the problem goes away.
