BC++4.5 --> 5.0 OWL no graphic display?

I was programming using Borland C++ 4.5 before. I write some programs using the OWL. Recently, I upgraded my Borland C++ to 5.0. I re-compile some of my program codes again and surprising, none of my programs display anything on the screen while I run those "new" files. The only thing displayed on the screen is the window frame and the title... can anyone tell me what is the problem? or did I do something wrong with my program codes? Below is the program code of  a simple program which displays a game board:

#include <owl\applicat.h>
#include <owl\framewin.h>
#include <owl\gdiobjec.h>
#include <owl\point.h>
#include <owl\dc.h>
#define LIMIT 5
#define EMPTY 0
#define BLACK 1
#define WHITE 2
class MyApp:public TApplication
{
public:
      MyApp():TApplication(){}
   void InitMainWindow();
};

class MyMainWndw:public TFrameWindow
{
public:
      MyMainWndw(TWindow *parent, const char far *title);

protected:
       UINT blockX, blockY, Chess[LIMIT][LIMIT];
   RECT rect;
   void Paint(TDC &paintDC, BOOL, TRect&);
   void EvSize(UINT, TSize &size);
   void EvLButtonDown(UINT, TPoint &point);
   void EvRButtonDown(UINT, TPoint &point);
   DECLARE_RESPONSE_TABLE(MyMainWndw);
};

DEFINE_RESPONSE_TABLE1(MyMainWndw, TFrameWindow)
      EV_WM_SIZE,
   EV_WM_LBUTTONDOWN,
   EV_WM_RBUTTONDOWN,
END_RESPONSE_TABLE;

MyMainWndw::MyMainWndw(TWindow  *parent, const char far *title):TFrameWindow(parent,title)
{
      for (int x=0; x<LIMIT;x++)
         for (int y=0; y<LIMIT; y++)
            Chess[x][y]=EMPTY;
}

void MyMainWndw::EvSize(UINT, TSize &size)
{
      blockX=size.cx/LIMIT;
   blockY=size.cy/LIMIT;
   Invalidate();
}

void MyMainWndw::EvLButtonDown(UINT,TPoint &point)
{
      int x=point.x/blockX;
   int y=point.y/blockY;
   if((x<LIMIT)&&(y<LIMIT))
   {
         MessageBeep(0);
      Chess[x][y]=BLACK;
      rect.left=x*blockX;
      rect.right=(x+1)*blockX;
      rect.top=y*blockY;
      rect.bottom=(y+1)*blockY;
      InvalidateRect(TRect(rect),FALSE);
      }
}

void MyMainWndw::EvRButtonDown(UINT,TPoint &point)
{
      int x=point.x/blockX;
   int y=point.y/blockY;
   if((x<LIMIT)&&(y<LIMIT))
   {
         MessageBeep(0);
      Chess[x][y]=WHITE;
      rect.left=x*blockX;
      rect.right=(x+1)*blockX;
      rect.top=y*blockY;
      rect.bottom=(y+1)*blockY;
      InvalidateRect(TRect(rect),FALSE);
      }
}

void MyMainWndw::Paint(TDC &paintDC, BOOL, TRect&)
{
      int x,y;
        char szBuffer[]="1233456";
   paintDC.TextOut(10,0,szBuffer);
   TBrush *BlackBrush=new TBrush(TColor::Black);
   TBrush *WhiteBrush=new TBrush(TColor::White);
   TPen *BlackPen=new TPen(TColor::Black);
   paintDC.SelectObject(*WhiteBrush);
   paintDC.SelectObject(*BlackPen);

   for( x=0; x<LIMIT;x++)
         for( y=0;y<LIMIT;y++)
            paintDC.Rectangle(x*blockX,y*blockY,(x+1)*blockX,
         (y+1)*blockY);

   for (x=0; x<LIMIT; x++)
            for(y=0;y<LIMIT;y++)
         {
               if (Chess[x][y]==BLACK)
                  paintDC.SelectObject(*BlackBrush);
            else if (Chess[x][y]==WHITE)
                  paintDC.SelectObject(*WhiteBrush);
                        if(Chess[x][y]!=EMPTY)
                  paintDC.Ellipse(x*blockX+1,y*blockY+1,(x+1)*blockX-1,(y+1)*blockY-1);
                  }
      delete BlackBrush;
   delete WhiteBrush;
   delete BlackPen;
}


void MyApp::InitMainWindow()
{
      TFrameWindow *wndw=new MyMainWndw(0, "Hit Test by Mouse");
   SetMainWindow(wndw);
}

int OwlMain(int, char*[])
{
      return MyApp().Run();
}