Comment 12 for bug 637676

It should be fine to have both installed (for instance if you have both xfce and gnome users). But a session manager should only start one of them. The xscreensaver package does not install a autostart desktop file for this reason. I believe the xfce session manager takes care of starting xscreensaver itself. I don't know if it starts gnome-screensaver also if it is installed.

In what kind of session did this problem happen? Xfce?