I am running Windows 7 and just yesterday the following message was displayed and I can't log into Firefox:
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.
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.
ყველა პასუხი (1)
This problem is caused when Firefox process does not exit even when you close the application. See if the solutions given in this article help: Firefox Hangs.