My program gets a WM_QUERYENDSESSION message and asks the user if it is OK
to shutdown.

While he's thinking about it, Windows displays a box saying the program is
not responding.

If the user clicks Cancel the shutdown is canceled.

My program receives a WM_ENDSESSION message and tells the user that the
shutdown has been canceled.

All OK except that my message box from the WM_QUERYENDSESSION is still being
displayed.

I can't come up with a procedure that is better than this.

Is it possible for me to close the messagebox?

Any suggestions?

Thanks