I've had this scenario: a form called another form, which showed some results in a grid. Grid was read-only in a way that it intercepted every KeyPress and reacted upon it (incremental search, navigation etc). It all worked just fine.

Then I decided I don't need the _screen at all, so made the first form desktop and hide the _screen:
desktop=.t.
showwindow=2
windowstate=2

It had some consequences to some other called forms, namely an Alert form (just another replacement for messagebox), which refused to appear until it got
windowstate=1
instead of default 0. As for the formset containing the form containing the grid, it also had to get windowstate=2, but its keypress doesn't get triggered anymore - the grid behaves just as a normal grid.
Before I get into excessive debugging (and I may guess that debugging a keypress event was always tricky), I'd like to know if anyone of you folks had a case like this.