How to replace gnome-screensaver with xscreensaver in ubuntu
On X11 systems, XScreenSaver is two things: it is both a large collection of screen savers; and it is also the framework for blanking and locking the screen.
You can remove gnome-screensaver using the following command from your terminal
sudo apt-get remove gnome-screensaver
You can install xscreensaver using the following command from your terminal
sudo apt-get install xscreensaver
You can start the xscreensaver executable to start the xscreensaver daemon.
xscreensaver-demo will show the xscreensaver's configuration dialog, the thing that you see in system>preferences.
Now that standby/suspend/screen off is controlled by gnome-screensaver and configured through the power manager(system>preferences), since it's disabled now, it won't work anymore, but other configuration (power button action etc...) will still work.
Configure your standby/suspend/screen off configuration form xscreensaver.
Next, you have to add the xscreensaver -nosplash at startup; to do so, goto system>prefferences>startup applications; there click add and after putting a name, add "xscreensaver -nosplash" in the command section.
To have all screensavers enabled run the following command from your terminal
sudo apt-get install unicode-screensaver xscreensaver-gl-extra rss-glx xscreensaver-data-extra
Via Ubuntu Forum