Em uma das páginas de suporte do Firefox , há um aviso de que -no-remote
nunca deve ser usado ao iniciar os perfis padrão .
You can also get this message if you try to open a link from an external program (e.g., double-click a link in an email or HTML file) and there is another instance running that uses the default profile and that was started with the -no-remote argument (or you have the environment variable
MOZ_NO_REMOTE=1
set). You should never use -no-remote to start the "default" profile. See Opening a new instance of your Mozilla application with another profile for more information.
E há outra explicação para esse problema:
Important: Never use -no-remote to start the "default" profile (the one that is set to open without asking when you launch Firefox). That's because when you launch Firefox, for example, by clicking a link in your mail program, you will get a Firefox is already running but is not responding message if the default profile is already in use. The solution is to always start the default profile normally and launch all others with -no-remote. Then it will work.