It's a minor upgrade, but the newest version of Thunderbird 3.1.2 is here.
Total bug fixes in this version of Thunderbird is seven.
For Mac users upgrading from 3.0.6, smart folders will no longer be empty by default - minor fix.
Upgrading from 3.0.6 broke IMAP folder notifications on Windows - that's been fixed.
Indexing is no longer broken on all operating systems running Thunderbird.
There are four more fixes, you can read about them here.You can download the newest version of Thunderbird here.