Please explain the problem in detail&#46; What happens? What is/are the exact error message(s) ? Type '''about:preferences#search'''<enter> in the address bar. You can select any search engine to be your default from here. You can also remove any engine from here.

You can check for recently installed suspicious or unknown extensions. 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 You can do a malware scan just to be sure. *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware