diff --git a/src/widgets/ProgressDialog.cpp b/src/widgets/ProgressDialog.cpp
index 72762ea7d..f6de2339e 100644
--- a/src/widgets/ProgressDialog.cpp
+++ b/src/widgets/ProgressDialog.cpp
@@ -37,6 +37,9 @@
 #include <wx/event.h>
 #include <wx/frame.h>
 #include <wx/intl.h>
+#if defined(__WXMAC__)
+#include <wx/menu.h>
+#endif
 #include <wx/settings.h>
 #include <wx/sizer.h>
 #include <wx/stopwatch.h>
@@ -1144,6 +1147,21 @@ ProgressDialog::ProgressDialog(const wxString & title, const wxString & message,
    // delay, we MUST disable other windows/menus anyway since we run the risk
    // of allowing other tasks to run before this one is complete.
    mDisable = new wxWindowDisabler(this);
+
+#if defined(__WXMAC__)
+   // LL:  On the Mac, the parent windows get disabled, but they still respond
+   //      to the close button being clicked and the application quit menu item
+   //      is still enabled.  We do not want the parent window to be destroyed
+   //      while we're active, so we have to kludge around a bit to keep this
+   //      from happening.
+   WindowRef windowRef = (WindowRef) MacGetWindowRef();
+   SetWindowModality( windowRef, kWindowModalityAppModal, NULL ) ;
+   BeginAppModalStateForWindow(windowRef);
+
+   wxMenuBar *bar = wxStaticCast(wxGetTopLevelParent(wxTheApp->GetTopWindow()), wxFrame)->GetMenuBar();
+   bar->Enable(wxID_PREFERENCES, false);
+   bar->Enable(wxID_EXIT, false);
+#endif
 }
 
 //
@@ -1158,10 +1176,18 @@ ProgressDialog::~ProgressDialog()
       Beep();
    }
 
+#if defined(__WXMAC__)
+   wxMenuBar *bar = wxStaticCast(wxGetTopLevelParent(wxTheApp->GetTopWindow()), wxFrame)->GetMenuBar();
+   bar->Enable(wxID_PREFERENCES, true);
+   bar->Enable(wxID_EXIT, true);
+
+   WindowRef windowRef = (WindowRef) MacGetWindowRef();
+   EndAppModalStateForWindow(windowRef);
+#endif
+
    if (mDisable)
    {
       delete mDisable;
-
    }
 
 #if defined(__WXGTK__)