When I click on the "close" button at the bottom of that box, a Windows dialog box will pop up telling me that Juno has created an invalid page fault or some such thing and will be shut down. The program will in fact shut down at that time.
The interesting thing is that, most of the time, I can continue to use Juno as long as I don't close that original dialog box. I'm doing it now. I can probably go for several more pages, before the whole thing crashes. I sometimes think that this dialog box IS the error. Man, computers are so freking weird!