I'm Back! ;-)
Today I'll decided to take few time to speak about a problem probably really common but maybe not so clear..
I myself had to fight to solve..
This Link I think that could solve most of all problems! But for a local permanent and short guide (..or breaking the link..) I decided to post below the most important things, so this excerpt :
First, backup your Profile ( http://kb.mozillazine.org/Profile_backup )
Create a new sub-folder under Local Folders. Move all of the messages currently in your Inbox to that new subfolder.
Confirm that you have made the recommended backup of your Profile.
Close Thunderbird and navigate to your Profile folder. Delete both the file Inbox.msf and the file Inbox with no extension.
Thunderbird and you should find a new, empty Inbox folder in place.
Copy any messages you MUST have in your Inbox from the sub-folder
created above to the Inbox. Compact the Inbox after those messages are
The "Real Fix" entry in this article -- http://kb.mozillazine.org/Compacting_folders#Real_fix also describes this process.
I hope this could be useful!!! Bye bye :-)
( http://forums.mozillazine.org/viewtopic.php?f=39&t=2247581 )