Maxime, is Thunderbird configured to automatically download new email when Thunderbird starts? Do you use a secure connection (e.g. SSL) to your email server? What happens if you don't automatically check for new email when Thunderbird starts, does the problem disappear?
Maxime, is Thunderbird configured to automatically download new email when Thunderbird starts? Do you use a secure connection (e.g. SSL) to your email server? What happens if you don't automatically check for new email when Thunderbird starts, does the problem disappear?
I'm thinking that this could be the same as bug 390036 and bug 428522.
I'm not sure that Lightning 0.8 is causing the problem. As I reported in one of those bugs, Lightning 0.7 can also show this behavior.