fullscreen window

[hamsterman]

Hi all,
I have problems with creating fullscreen windows.
Generally it works, but
When I call GetOpenFileName the dialog never shows up. My window remains on the top.
If the app crashes, I can't close it. Again, it stays on the top, even above task manager...
I suppose the problem is with my window style.
When creating a window, my dwStyle = WS_POPUP and dwExStyle = 0.