As a workaround kill the Firefox and any related processes e.g. plugincontainer.exe using for instance task manager * [["Firefox is already running but is not responding" error message - How to fix it]] '''IF'''' you have Firefox set to clear History at close down it is probably a known bug. Set Firefox to remember History. * New Button -> Preferences -> |Privacy| History Firefox will [Remember History v]] You can use Private Browsing Windows if it helps, but you may need to close these before closing down Firefox * [[Private Browsing - Browse the web without saving information about the sites you visit]] The bug is being worked on. if you do not wish to wait for the fix to get to the Release There is a possible fix in the Beta channel version of Firefox * http://www.mozilla.org/en-US/firefox/channel/#beta/beta-desktop (If you consider installing that do NOT use any option that deletes personal information; do not delete the profile - In fact there is no need to uninstall Fx29 just install Fx30 over the top of it)