I have noticed that there are times both when opening and when closing that Lacerte sends up a 2nd screen that is behind the main screen. I finally learned to use Alt + Tab to be able to see the open screens and find the miscreant pain in the patootie screen that Lacerte though was so imported for me to see hidden in the bowels. 

Alternatively just use Ctrl + Alt + Del to start taskbar to close Lacerte, which should also close that other bothersome pest.