Bill,
No, there's no
good reason they need _screen to be visible, fortunately it doesn't have to be within visible coordinates. IMHO they should be In Top Window, so there isn't really any difference between app that run as a top-level form or inside _screen. I'm not sure desktop is right because it wouldn't minimize with the app.
>I found this gotcha while developing a small utility not too long ago. :-) It seems to me the "system" dialogs should be of "desktop" type, not requiring a visible application desktop to display on their own accord. Do you happen to know why they do?