1.In a terminal window run: gconf-editor
2.Navigate to apps > gnome-screensaver
3.Go down to: themes
4.Right click then select: Unset Key
Your screen saver will now be the "blank" default.
Note: you maybe able to find gconf-editor under Applications > System Tools > Configuration Editor. This just saves you opening a Terminal window.
Thanks to SteveDee for this tip!