< snip >
>>>>>
>>>>>I added _screen.visible = .t. to my environment setup routine and its fixed. I still don't know how it broke!
>>>>>
>>>>>At one time I had access to the properties window with the _SCREEN object having focus. I can't seem to get this back.
>>>>>
>>>>>I'm thinking that I inadvertently set the VISIBLE property of the _SCREEN object to .f., and it is stored somewhere, resulting in the unexplained behaviour of my exe.
>>>>
>>>>You can get to the _screen object properties sheet by opening Properties window when there are no visual designers open.
>>>
>>>Thanks for the reply Sergey.
>>>
>>>How do I open the Properties window with no visual designers open?
>>>
>>
>>Click on the properties button on the toolbar or go to menu Window -> Properties Window.
>
>Thanks again for the reply, Sergey. I looked in vain for the properties button on the toolbar (not visible) and then found the Properties Window under the Window menu. I have subsequently found that I had to turn on the "Standard" toolbar to get the Properties button back.
>
>How can I programmatically open a specific toolbar?

AFAIK, you cannot. However, after you open it manualy you can hide and show it.

Hide Window ( "Standard")
Show Window ( "Standard")