Yes you are forgetting something. When the screensaver becomes active (or if you select it and choose “example” in the display properties) the screensaver will start running as a process. And it keeps running even if you set the screensaver properties to use none. This was a bug in 4.1 and still isn’t solved in 4.5 (at least here it is not working properly)

See also http://forum.avast.com/index.php?board=1;action=display;threadid=6559