User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8 Build Identifier: Thunderbird/3.1.2 Master Password: You can pass the Master Password if you klick "Cancel" twice in the blank Password Required field. So the Master Password serves for nothing... Reproducible: Always Expected Results: Insist in filling in the required Master Password.

The purpose of the Master Password is to protect saved passwords by encrypting them on disk. It is not designed to block access to your mail or browser: http://support.mozilla.com/en-US/kb/Protecting%20stored%20passwords%20using%20a%20master%20password

The master password protects your server passwords, so you won't be able to get or send new mail. If you need to protect your local files you need to use the operating system features to do so. There may be some add-ons that can give you part of what you want, please see the Thunderbird support site.