I was able to reproduce this error manually on Firefox 9.0.1 using Ubuntu 10.04. I simply double-clicked the Firefox icon twice quicker than I ever normally would, and the Close Firefox error appears: "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."
I was able to reproduce this error manually on Firefox 9.0.1 using Ubuntu 10.04. I simply double-clicked the Firefox icon twice quicker than I ever normally would, and the Close Firefox error appears: "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."