Thunderbird will not open. the error message is: "Thunderbird is already running, but is not responding. The old Thunderbird process must be closed to open a new window." Pressed the "Close Thunderbird" button, but no response. Checked Task Manager and ended the Thunderbird application...still no change. Uninstalled Thunderbird and downloaded .exe file and installed...still the same error message. Rebooted the computer...still not change. Can you please assist with this problem. Thankyou I