can't switch to app ?

D3, W95 - I have an app which does not display in the task bar, instead
it has a tray icon (uses RX Lib component).  Clicking on the tray icon
restores it (if it was minimized) and Brings to Front (if it was behind
another app.)

so far, so good.

Now I added a button which calls a showmodal form.  On the showmodal
form, a button starts a process which has a loop.  The loop is short,
but repeated many times, so it is usually lengthy.  The loop includes
Application.ProcessMessages.

Problem:  if, while the above process is running, the user switches to
another app on the task bar, or starts another app, he cannot switch
back to my app by clicking on the tray icon - nothing happens!

Why is this;  how can I fix it?

Thanks,
Glenn