This issue can be caused by an extension that isn't working properly.<br /> You can try to disable all extension to see if it still happens. *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes If it works in Safe mode or with all extensions (Tools > Add-ons > Extensions) disabled then try to find which is causing it by enabling one extension at a time until the problem reappears. Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") ---- You can also check for issues caused by DDE. *http://kb.mozillazine.org/Windows_error_opening_Internet_shortcut_or_local_HTML_file_-_Firefox