Comment 18 for bug 988290

If this issue is now known to be in gnome-screensaver and to be independent of the graphics card/driver used by X, I'd think it might help to edit the "Affects" stuff to reflect these facts :) I'd update it, but I have not tested / duplicated the issue myself, and so I don't feel I should be doing that.

Note that simply uninstalling gnome-screensaver might well be a valid workaround for this issue in some cases -- just push the power button on your monitor when you walk away from it.