>If I do not Hide the VFP screen, everything works OK. I would be satisfied with simply having modal behavior without hiding the menu screen. BUt I can't make it work with the VFP screen hidden.

Sorry, I can't guess what might be happening. I have several apps that use top-level forms, and the modal forms within run just fine.

Can you build a simple app with a simple menu and a single form, and reproduce this? I have tried, and my app behaves as expected.