Firefox does not open in more than one virtual desktop of sysinternals' Desktops utility
sysinternals' Desktops utility creates 4 virtual desktops on a Windows machine, available here: http://technet.microsoft.com/en-us/sysinternals/cc817881
when Firefox is open in one such virtual desktop, it fails to open in another, giving the message "Firefox is already running, but is not responding. to open a new window, you must first close the existing Firefox process or restart your system."