Comment 6 for bug 117482

I had the same issue. Reformatting and reinstalling, in this case, is like killing a fly with a nuclear weapon.

Restart your machine, then edit the following file in a text editor:

/home/(your-username-here)/.gconf/apps/gnome-screensaver/%gconf.xml

Change the value under the them section to use a non-buggy screensaver, e.g.

<stringvalue>screensavers-endgame</stringvalue>

Now save and close the file, then start the Screensaver app, it will be on the one you specified and you are free to choose others. Just don't pick the molecule one again!