Comment 7 for bug 280987

This is still present in Thunderbird 2.0

In detail:

When starting Thunderbird offline the Master password is requested after some time. The time it takes to see the request is determined bu the "Check new messages every X minutes" option in the account section.

What seems to happen is that even when offline, the process for connecting to server is still triggered and the Master password request pops-up. This can be very annoying if the user has several accounts, since the password is requested every time the timing cycle goes by. However if the master password is correctly inserted, this window no longer appears until restart.

Also if you then change to online, you won't need to insert the password again.

Hope this helps to clarify the problem