mplayer stop XScreenSaver ignored

[Dj YB]

hello list,
I am using fedora 11 
mplayer version SVN-r29701-4.4.1 
(but the problem appeared in earlier versions as well)
NVIDIA driver version 190.42
X server version number 11.0
server vendor version 1.6.3.901 (10603901)
NV control version 1.20

I have toggled "stop XScreenSaver" in mplayer misc tab
and my screen saver is still running while mplayer is playing in full screen.
please advise...
thanks,
YB.