Today I noticed a new problem on my MacBook Pro. I selected a group of messages and tried to move them to a new folder using drag and drop. No matter how many or how few I select, only one email is moved. I tried a few different actions and noticed that similarly I can only delete one email at a time. All actions on a multiple selection are only being operated on one item. I've tried closing and reopening Thunderbird and rebooting the computer. I have moved emails in this manor countless times in the past with no problem.