EnumThreadWindows - EnumThreadWndProc does not get called

I am using EnumThreadWindows to enumerate all windows of newly created
process using CreateProcess. EnumThreadWndProc gets called for notepad
but does not get called for MS Word. I am not able to figure out why it
is happening, Here is piece of code.

STARTUPINFO si;
PROCESS_INFORMATION pi;

ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );

    // Start the child process.
    if( !CreateProcess( TEXT("C:\\Program Files\\Microsoft
Office\\OFFICE11\\winword.exe"), NULL,NULL,NULL,FALSE,FALSE,0,NULL,NULL,&si,&pi
)
    )
    {
        printf( "CreateProcess failed (%d).\n", GetLastError() );
        return;
    }
    Sleep(10000);
    WaitForInputIdle(pi.hProcess,10000);

    // Enumerate all threads of Windows
   BOOL bRetVal =
EnumThreadWindows(pi.dwThreadId,EnumThreadWndProc,(LONG)this);

   if(! this->m_hWnd )
   return;

BOOL CALLBACK EnumThreadWndProc(HWND hwnd,LPARAM lParam)
{
      CMainFrame *pFrameWnd = (CMainFrame*)lParam;
      if(GetMenu(hwnd) != NULL)
      {
   pFrameWnd->m_hWnd = hwnd;
    return FALSE;
      }
    return TRUE;
}

Thanks ,
Ajay