I recently installed Ubuntu 6.10 (Edgy Eft) on an extra PC. Before that I tried to install Suse Linux Enterprise Edition (SLED) but it couldn't handle the video properly. I am very impressed with Ubuntu's ability to handle hardware. Even when it can't handle the hardware it seems to do something intelligent about it like...not crashing.
I found that some of the many Gnome screensavers ran poorly on this old PC and one (GLBlur) caused a hard lockup. The Screensaver Preference dialog is almost useless in terms of individual screen saver configuration. Seeing as I wanted to use the Random screen saver function but didn't want hard lockups randomly I figured I'd have to dig around in the terminal. Whoopdy-doo.
Disabling Gnome screen savers
I tried man pages and Google for info on the subject but didn't find anything helpful. The Gnome-Screensaver website didn't talk about this either.
Open a terminal.
Find the place where your screen savers are located. I used the locate command to find 'glblur' (or some other screensaver in your list). In the results I found /usr/share/applications/screensavers/glblur.desktop. This looked promising (yes, I know this isn't the "screensaver" but just a config file, thank you Linux expert. Where were you when my PC was hard locking? Huh? Huh?)
So, in the past, I've found that removing files often helps track down what I'm looking for because if something else needs it then it will probably complain (and as I'm not removing the kernel or anything it shouldn't blow up my installation, but even if it does that's how I learn my lesson).
Rename glblur.desktop to glblur.desktop.disabled. You'll have to use sudo. Repeat for any other screensavers you'd like to see disappear.
Now when you open the very useful Screensaver preferences GUI those 'disabled' screen savers will no longer be able to save your screen.