XFCE4 Xscreensaver4.07 and video problem
 

HI all.
I have some little problem that I can't solve. These days I had changed my windows manager from enlightenment to XFCE 4.0. I have disabled screensaver now because when I'm going to watch some movie, screensaver can't detect that video is running, and it starts after setted minutes.
In enlightenment screensaver workes normally of course.
Does anybody know how to set xscreensaver 4.07 to good detecting of video running?
Please help
Thanks