mode change moves windows

Hi im working a prog that can switch between fullscreen and windowed mode. every time i switch from fullscreen to windows mode or exit from fullscreen mode i find that all the windows that are open have moved down and to the right. ive noticed this with several games and my own apps. i have also noticed that this dose not happen to all fullscreen app. dose anybody know what causes this and how to avoid it??? any ideas would be greate even if its not a solution

- Jono AH