Comment 10 for bug 49441

to disable the offending screensaver in ubuntu just remove the execute attribute from the files.

for gnome screensaver:
cd /usr/lib/gnome-screensaver/gnome-screensaver
sudo chmod -x *

for xscreensaver:
cd /usr/lib/xscreensaver
sudo chmod -x *

both sets of screensavers will not be displayed in the list of available screensavers any more, for any user.