Background: QuickWin GUI code compiled with DF 6.0 on an XP system runs on my own Win7 system, but not on any other. Now a coleague in the UK has succeded in compiling with a current version of IVF, with the same bad result.
This code segment works properly in all cases:

      USE       DFLIB
      USE       DFLOGM
      TYPE (dialog)       DBOX0, DBOX1
100   CONTINUE
      LNEW = .FALSE.
      LOLD = .FALSE.
      MENUCODE = 0
      DO WHILE (.NOT.LNEW .AND. .NOT.LOLD)
!        Twiddle thumbs at 10Hz while waiting for menu selection
         CALL SLEEPQQ(100)
      END DO

Flags LNEW and LOLD are set in callback routines for mouse clicks on particular menu entries. Every callback routine also sets a specific value for MENUCODE.

However, the following code does not work in newer Win7 systems:

200   CONTINUE
      PRINT *, 'Waiting for Menu Selection . . .'
      LADD      = .FALSE.
      LEDIT     = .FALSE.
      LDELETE   = .FALSE.
      LVARY     = .FALSE.
      LVLIST    = .FALSE.
      LCNNCTIO  = .FALSE.
      LSRRND    = .FALSE.
      LSAVE     = .FALSE.
      LSAVEAS   = .FALSE.
      LGEOMETRY = .FALSE.
      LMULTIGEO = .FALSE.
      L3DVIEW   = .FALSE.
      MENUCODE  = 0
      DO WHILE (MENUCODE .EQ. 0)
!        Another 10Hz twiddle while waiting for Menu selection
         CALL SLEEPQQ(100)
      END DO

Nothing ever sets a MENUCODE, so the loop is infinite (requires using taskbar to terminate). In fact, by the time execution reaches this point the Frame Window no longer responds to the mouse at all. The window can not be dragged, and never becomes active. What can I have done to lose all control of the Frame Window?  The intervening code between these two wait-for-menu loops includes a MESSAGEBOXQQ window and also a sinple text Dialog Box. Both of these "appear" to work in all systems:

      IF (LNEW) THEN
         IF (FLAG) THEN
            IF (MESSAGEBOXQQ('Overwrite existing file?'C,               &
     &            FileName, MB$OKCANCEL) .EQ. MB$IDCANCEL) THEN
               LNEW = .FALSE.
               GO TO 100
            END IF
         ELSE
!           Is the directory valid?
            OPEN (2, FILE=FileName, IOSTAT=IERR)
            IF (IERR .NE. 0) THEN
               PRINT *, FileName(1:IDOT+4)
               STOP '*** Can''t open above file - check Directory.'
            END IF
            CLOSE (2)
         END IF
!
!        Use text dialog box to get new Title
         FLAG = DLGINIT(IDD_DIALOG0, DBOX0)
         FLAG = DLGSET(DBOX0, IDC_List_Title,                           &
     &                 'Enter Title for first line of output files')
         FLAG = DLGSET(DBOX0, IDC_EDIT1, GeoFile(1:IDOT+3))
         ISTAT = DLGMODAL(DBOX0)
         IF (ISTAT .EQ. IDOK) FLAG = DLGGET(DBOX0,IDC_EDIT1,DESCRIP(1))
         CALL DLGUNINIT(DBOX0)

[similar code in the "LOLD" option]

Print statements after this point (up to and including the Print at statement 200) appear correctly in the control window. Does anyone have a suggestion for tracking this down? Perhaps the most confusing feature is that the code with the old compiler works on at least one Win7 system, but neither the old nor the new compiler generates code that works on most Win7 systems.

Thanks!