Conflict with Firefox on Mac OS Mavericks: Open new FF window fails
Mac OS Mavericks (10.9.1) HTTPS-Everywhere 3.4.5 Firefox 27 and Firefox 28 Beta
If Firefox is open but NO window is displayed and HTTPS-Everywhere is enabled, it is not possible to open a new window by any method.
Workaround: Quit Firefox and relaunch by clicking on a URL icon; Firefox launches and opens a new window. If the window is closed later, ALL methods for opening a new window work until FF is quit.
Disabling HTTP-Everywhere restores normal behaviour to Firefox.