amazing function behavior

[Zarathustra]

I resolved my access violation problem by including at the begin of wndProc inside Window class, the following code:
//____________________________________________________
  private dword wndProc(ptr o_hwnd, dword o_msg, ...
  {
    asm{
      push 0x00000000;
      push [o_hwnd];
      call [user32.getWindowLong];
      mov  [EBP - 0x04], EAX;
    }

    switch(o_msg){
      ...
  }
//____________________________________________________