I do not know what happened, but Thunderbird will not open. I get the following message in the Close Thunderbird window that pops up every time it tries to open. "Thunderbird is already running, but is not responding. The old Thunderbird process must be closed to open a new window." How do I fix this? How is the "old" Thunderbird closed? I have closed, opened, rebooted, uninstalled, reinstalled many times with no luck. Please give me some clue how to get my email back up and not lose all my messaged. Thank you. Bill