Mozilla Messaging has release the first update for Thunderbird 3.0. The new Thunderbird 3.0.1 update includes these changes:

• Several fixes to improve stability and security
• Several fixes to the user interface and attachment handling. For a more detailed list of bug fixes, see the Rumbling Edge.

Thunderbird 2.0 and older users should upgrade by downloading Thunderbird 3.0.1 directly via http://getthunderbird.com. Thunderbird 3.0 users should be prompted to update within the next 48-hours or can do so manually via Help >> Check For Updates…

Source: Mozilla Developers News