CLOSE FIREFOX "Firefox is already running, but is not responding.  The old Firefox process must be closed to open a new window."

                    PROFILE MISSING "Your Firefox profile cannot be loaded.  It may be missing or inaccessible."

Firefox will neither stop nor start. I have attempted to start it in both normal and safe mode, but I get the same results. I receive the following two messages: CLOSE FIREFOX "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." When I select either Cancel or Close Firefox this, it is followed by PROFILE MISSING "Your Firefox profile cannot be loaded. It may be missing or inaccessible." I have uninstalled and re-installed Firefox. Same result. I have uninstalled, cleared the registry and re-installed. Same result. I am at a complete loss as to what to do next.