I have migrated Thunderbird to a new computer (both running Windows 10, Thunderbird on both 78.10.0) by a fresh install, then moved the Thunderbird folder as described in the support pages. First start of Thunderbird everything worked absolutely fine. Mails and archives were there, receiving and sending also ok. On the second start of Thunderbird there only appeared some sort of "default" more or less blank window, with no accounts, no mails and even without any dropdown menues. Task manager reported no further cpu activity of Thunderbird. I have tried several times, even again a fresh install, but doesn't help. Same effect, first start ok, second fail. Also tried with antivirus off. No change. What can I do? Michael