Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

Memory leaks can be caused by an extension that isn't designed properly. You can check the Firefox Task Manager (about:performance) and about:memory pages. *https://support.mozilla.org/en-US/kb/task-manager-tabs-or-extensions-are-slowing-firefox *https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-or-cpu-resources ---- Start Firefox in <b>Safe Mode</b> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <b>hardware acceleration</b> or <b>userChrome.css</b> is causing the problem. *switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes *do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems