Recently My Thunderbird stuck somewhere, and refused to start saying – Thunderbird already running. Close the process to restart or reboot your computer. I rebooted, tried to fix with reinstallation but failed. A quick search at Internet advised to remove .lock or parent.lock file under %APPDATA% directory. But I did not find one in my computer. Now what to do?
I simply removed profile.ini file under %APPDATA%Thunderbird directory, and restarted thunderbird. Voila, it fixed the problem.