I updated my Mozilla today and, after I closed it the last time, it just won't let me reopen. It shows a warning window saying: "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." I even shutted down and restarted my laptop, but it keeps giving me this same message when I try to open Mozilla. I unistalled, reinstalled... still the same warning. Tried both close and cancel buttons, none worked to change a thing, nothing happens.