Thunderbird: How to reset your masterpassword
Forgot your masterpassword?
Or did it ask you for one, even if you didn’t have/weren’t using one before, after updating to version 3, like it did for me?
I finally found the solution to my problem: http://kb.mozillazine.org/Master_password#Removing_your_master_password
Choose Tools – Error Console, paste the expression: openDialog(“chrome://pippki/content/resetpassword.xul”)