I am testing a VB6 application for compatibility as we move to Windows 7 64-bit desktops in 2014.

I have noticed something that is very strange and can't work out why it's happening.

When I open certain child forms in my MDI interface, the application MDI window disapperas, and is also not in the Task List in Task Manager. The child form that I opened is fine, I can interact with, use global ADO connection variables and settings variables that are in the scope of the MDI parent, and I can do db changes.

When I close the child form, there is no MDI parent/ application windiow, and I have to clsoe the process using Task Manager.

Here is the code used to open the child form (from a menu in the MDI parent):

Code:
 Private Sub mnuHermesDataInputProvisions_Click()
         Me.MousePointer = vbHourglass
         Load frmInputProvisions
         frmInputProvisions.Show vbModal
         Me.MousePointer = vbDefault
    End Sub
Here is the form load event handler in the child form:

Code:
 Private Sub Form_Load()
     With Me.DTPdataDate
          .Format = dtpCustom
          .CustomFormat = "dd MMM yyy" 'DTPICKER_DATE_FORMAT '"dd MMM yyy"
       End With
       Me.Top = frmMain.Top + (frmMain.Height - frmMain.ScaleHeight)
          
       Call mSetMaxLength
       Call mRefreshDataRecordset
       Call mSetVisible(False)
       Call mSetLocked(True)
       Call mFormatStatusBar
       Call mConstructListView
       Call mPopulateListView
       Call mSetTxtBoxValues
       Call mSetEnabled(True)
       mliNewIndex = 0
       mbAddNew = False
       
       mbAscendingSort = False
       
       frmMain.MousePointer = vbDefault
    End Sub
Has anyone seen anything similar happening with VB6 MDI applications under Win 7 64 bit?

Any thoughts on what I can do to prevent this - is there any documentation from Microsoft about this?

thanks
Philip