Issues with tooltips not working properly have been reported to be caused by the Google Toolbar (Tools > Add-ons > Extensions) You can check if there is an update available that fixes that issue. You can try to uninstall and reinstall the latest GT, that has been reported to work. * http://www.google.com/tools/firefox/toolbar/FT5/intl/en/ * http://tools.google.com/tools/firefox/toolbar/FT5/intl/en/install.html