COleSafeArray / VARIANT memory leak?

Question

I want to export a lot of (table) data to Excel. I'm developing on Windows Xp, Vs2005. I'm filling a COleSafeArray, which was initialized like this:

safeArray.Create( VT_VARIANT, 2, numElements ); // 2 dimensional, 30000 rows, 3 columns

Now the filling is really fast, but in TaskManager/Process Explorer/VMMap, it looks like some of the memory does not get released properly (VMMap still finds my dummy strings in the memory). I tried the tips (disabling BSTR caching) from the following pages, but had no success so far:
http://blogs.msdn.com/oldnewthing/archive/2009/11/27/9929238.aspx
http://blogs.msdn.com/larryosterman/archive/2004/09/28/235304.aspx

Is there still the caching taking place (I've set the environment variable OANOCACHE = 1), or is there something wrong with my code?

Note: This is part of a MFC dialog based non-unicode application.

//-----------------------------------------------------------------------------
template< typename _ValueType >
void setSafeArrayElement( const _ValueType& value, 
                          const int row, 
                          const int column, 
                          COleSafeArray& safeArray
                         )
{
  VARIANT variant;
  VariantInit(&variant);
  {
    COleVariant oleVariant = value;  
    variant = oleVariant;
    oleVariant.Detach();
  }
  long coordinates[2] = { row, column };
  safeArray.PutElement( coordinates, &variant );
  VariantClear(&variant);
}

//-----------------------------------------------------------------------------
#define XL_CELLTYPE_TEXT        "@"
#define XL_CELLTYPE_DOUBLE2     "#'##0.00"
#define XL_CELLTYPE_DOUBLE3     "#'##0.000"
#define XL_CELLTYPE_DOUBLE4     "#'##0.0000"
#define XL_CELLTYPE_DOUBLE6     "#'##0.000000"
#define XL_CELLTYPE_DOUBLE8     "#'##0.00000000"
#define XL_CELLTYPE_NUMBER      "0"
#define XL_CELLTYPE_NUMBER1000  "#'##0"
#define XL_CELLTYPE_DATE        "TT.MM.JJJJ"
#define XL_CELLTYPE_GENERAL     "Standard"

//-----------------------------------------------------------------------------
void CexcelTestDlg::OnBnClickedButton2()
{
  const bool closeExcel = true;
  const int rows = 30000;
  const int columns = 3;

  //AfxOleGetMessageFilter()->SetMessagePendingDelay( x );
  AfxOleGetMessageFilter()->EnableNotRespondingDialog( FALSE );
  AfxOleGetMessageFilter()->EnableBusyDialog( FALSE );

  Excel11::_ApplicationPtr    app;
  Excel11::WorkbooksPtr       books;
  Excel11::_WorkbookPtr       book;
  Excel11::SheetsPtr          sheets;
  Excel11::_WorksheetPtr      sheet;
  app.CreateInstance( "Excel.Application" );
  try
  {
    //app->Visible        = VARIANT_TRUE;
    app->Visible        = VARIANT_FALSE;
    app->Interactive    = VARIANT_FALSE;
    app->UserControl    = VARIANT_FALSE;
    app->ScreenUpdating = VARIANT_FALSE;
    app->DisplayAlerts  = VARIANT_FALSE;
    books           = app->GetWorkbooks();    // all open files
    book            = books->Add();           // add new file
    sheets          = book->Sheets;           // all worksheets

    try 
    {
      COleSafeArray safeArray;
      DWORD numElements[] = { rows, columns };
      safeArray.Create( VT_VARIANT, 2, numElements );

      // rename default worksheet
      Excel11::_WorksheetPtr
      sheet1          = sheets->GetItem(1);
      sheet1->Name    = "Blah"; 

      // format columns
      {
        std::string coords = getExcelCoordinates( 0, 0 );   // getExcelCoordinates returns strings like "A1", "F23", ... (excel cell coordinates)
        Excel11::RangePtr range = sheet1->Range[coords.c_str()][coords.c_str()];
        range = range->EntireColumn;
        range->NumberFormat = XL_CELLTYPE_TEXT;

        coords = getExcelCoordinates( 0, 1 );
        range = sheet1->Range[coords.c_str()][coords.c_str()];
        range = range->EntireColumn;
        range->NumberFormat = XL_CELLTYPE_DATE;

        coords = getExcelCoordinates( 0, 2 );
        range = sheet1->Range[coords.c_str()][coords.c_str()];
        range = range->EntireColumn;
        range->NumberFormat = XL_CELLTYPE_DOUBLE2;
      }

      // fill line by line
      for( int row = 0; row < rows; ++row )
      {        
        CString rowName;
        rowName.Format( "%d", row + 1 );        
        // Text
        CString v0 = CString( "Wusel Dusel " ) + rowName;
        setSafeArrayElement( v0, row, 0, safeArray );        
        // Date
        CString v1 = "11.12.1975";
        setSafeArrayElement( v1, row, 1, safeArray );
        // Number
        double v2 = 123.45;
        setSafeArrayElement( v2, row, 2, safeArray );
      }

      // export safearray to excel
      if( rows )
      {
        const std::string   cellCoordTopLeft      = getExcelCoordinates( 0, 0 );
        const std::string   cellCoordBottomRight  = getExcelCoordinates( rows-1, columns-1 );

        Excel11::RangePtr range = sheet1->Range[ cellCoordTopLeft.c_str(), cellCoordBottomRight.c_str()];      
        COleVariant         vtOptional((long)DISP_E_PARAMNOTFOUND,VT_ERROR);
        // export the whole safeArray contents to excel
        range->PutValue( vtOptional, COleVariant( safeArray ) );
      }

      // optimize column widths
      Excel11::RangePtr cells = sheet1->Cells;
      cells->Select();
      cells->EntireColumn->AutoFit();
      Excel11::RangePtr singleCell = sheet1->Range["A1"]["A1"];
      singleCell->Select();

      // clear safeArray
      VARIANT* varPtr = 0;
      try 
      {
        // Get a pointer to the elements of the array
        // and increments the lock count on the array
        safeArray.AccessData((LPVOID*)&varPtr);
        for( int i = 0; i < rows * columns; ++i )
        {
          VARIANT& vp = varPtr[i];
          VariantClear( &vp );
        }
        //decrement lock count
        safeArray.UnaccessData();
      }
      catch (COleException *pEx)
      {
        AfxThrowOleDispatchException(1003, _T("Unexpected Failure in FastSort method"));
        pEx->Delete();
      }
      //safeArray.DestroyData();            //???
      //safeArray.DestroyDescriptor();    //???  
      safeArray.Clear();
    }
    catch( std::exception& err )
    {
      MessageBox( err.what() );
    }

    if( closeExcel )
    {
      book->Close( VARIANT_FALSE );   // close the file
      app->Quit();                    // close Excel instance
    }
    else
    {
      app->Visible        = VARIANT_TRUE;
      app->Interactive    = VARIANT_TRUE;
      app->UserControl    = VARIANT_TRUE;
      app->ScreenUpdating = VARIANT_TRUE;
      app->DisplayAlerts  = VARIANT_TRUE;
    }
    app.Release();
  }
  catch( _com_error& err )
  {
    CString s(err.Description().GetBSTR());
    MessageBox(s);
  }

}