Thunderbird 6.0.2 has not yet been officially released but should be later today.
Download 6.0.2: Windows EN-US version, all other versions.
No release notes yet but I am assuming it is related to the issue in the Firefox 6.0.2 release notes (see post below).
*edit – 1547hrs
Thunderbird 6.0.2 is now official. Download or update from within the program.
The latest version of Thunderbird has the following changes:
– Removed trust exceptions for certificates issued by Staat der Nederlanden (see bug 683449 and the security advisory)
– Resolved an issue with gov.uk websites (see bug 669792)