Recently migrated a client from XP to 8.1. Installed Thunderbird 31.1.1 and created email account. Transfered message store files from XP computer with Thunderbird 24. Old folders and emails imported and appeared fine and were accessible but all of the old imported folders can not be rearranged or moved as an entire folder in Thunderbird 31.1.1. Can successfully rearrange the folders on a different computer running Thunderbird 24.