I've tried to reinstall the TB, but it seems like the problems still occur. After searching and looking for the solutions, I think this URL solve the problem:
How to fix it:
2. Open the Windows Start menu
3. In the "Search programs and files" box, type in %APPDATA%
4. Click the "Roaming" item that appears on the menu
5. In the Windows Explorer windows, choose Thunderbird > Profiles
6. Find and remove "folderTree.json",
7. Restart TB... That fixes it...