You can try to disable hardware acceleration in Firefox. *Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" You need to close and restart Firefox after toggling this setting. *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes You can check if there is an update for your graphics display driver and check for hardware acceleration related issues. *https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration Create a new profile as a test to check if your current profile is causing the problem. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox ----- Note that you can disable warning if you want to keep using your current profile by setting the browser.slowStartup.notificationDisabled to true on the <b>about:config</b> page. *https://support.mozilla.org/kb/firefox-takes-long-time-start-up