Hi geneo3711, <br/> sorry you are having problems. There are many possible reasons for problems lets look first at the ones I consider most likely: In ordinary circumstances Firefox only runs one instance using one profile. If you have Firefox not shutting down properly that may prevent you from starting Fifrefox until you have found and killed the process. (Also look for plugincontainer which may also exist). If you are certain Firefox is not already running then the problem is often that a Firewall or security related program is blocking Firefox. This is especially likely if you have installed new security software ,a new version of Firefox, or have tried to restore the computer. See also * [[Configure firewalls so that Firefox can access the Internet]] *[["Firefox is already running but is not responding" error message - How to fix it]] *[[Firefox won't start - find solutions]] *[[Troubleshoot Firefox issues using Safe Mode]] ** much more detail including command line details <br/> http://kb.mozillazine.org/Safe_Mode <br/> http://kb.mozillazine.org/Command_line_arguments Note on the command line options you may need to *enclose most of the line within quotes * include a space before the -p or -safe-mode