First excuse my bad english !
I'm just tried DO.
When DO is open, and I want to open an other application (Winamp or other), the window of the second application are in background and if I want to see this application, I does close or reduce DO windows.
Is it possible to open an other program in foreground windows (over) DO ?
You have probably clicked the pin button in the top-right corner, which forces the window to be on top:
Toggle the state of the pin buttons in the Opus Lister titlebars. Have a read of the manual: The Lister -> Window Buttons
Edit: Damn ... beaten!
Thanks so much !