As mentioned above, Thunderbird has been recently updated to 3.1.7 in Lucid (10.04 LTS). I confirm the observations of Matthias (#23): the issue still persists, though it's now less annoying, as the error message is handled/displayed by Ubuntu's notification subsystem, which at least doesn't require to take any further action by the user. Personally, however, I wouldn't consider the issue as resolved.
As mentioned above, Thunderbird has been recently updated to 3.1.7 in Lucid (10.04 LTS). I confirm the observations of Matthias (#23): the issue still persists, though it's now less annoying, as the error message is handled/displayed by Ubuntu's notification subsystem, which at least doesn't require to take any further action by the user. Personally, however, I wouldn't consider the issue as resolved.