Clicking on Compose or reply and even creating a calender item the window that should appear is not shown. I found it outside the screen and it was very small. Bij moving to the thunderbird taskbar item and then with the right mouse button on the miniscreen of the compose window with maximize it is there again. usually after that none of the menubar buttons works anymore. It looks like there blocked because of the other window with is already gone. I have to restart Thunderbird for that.