I just upgraded Thunderbird to 6.0.2.
The first notice I get is that the Enigmail addon is out-of-date.
So I downloaded the new one... 1.32... at least so I thought.
But I found out really quick that the Enigmail 1.32 download is corrupt.
Instead of 3.2Mb you just get about 0.5Mb....
http://enigmail.mozdev.org/home/index.php.html
...so I just downgraded back to 3.1.15...
The Enigmail 1.32 download is now corrected.
So I upgraded Thunderbird from 3.1.15 to 6.0.2.
Version 7 has to pass all the "testuser" out there.