Put your answers to these questions in a bug report or in a [http://getsatisfaction.com/mozilla_messaging/topics/new posting to support]:
# Does Thunderbird hang ... :
#* when started in [https://support.mozillamessagingmozilla.comorg/en-US/kb/Safe+Mode safe-mode safe mode]? If it doesn't hang in safe mode then disable add-ons until you find which add-on is causing the problem, then contact the add-on author.
#** happen without calendar/lightning extension? ({{Bug|532435}})
#** happen without enigmail extension?