From the looks of it (more than one application affected), it seems gnome screensaver may be doing something wrong regarding the new inhibition system (as suggested by seb in https://bugs.launchpad.net/ubuntu/+source/totem/+bug/448438): 

Totem Bug #598173
EoG Bug #599139

Since I'm not sure which part is the problem, filing a bug on gnome-screensaver too, so you can take a look.

Furthermore:

jeff@kusanagi:~$ gnome-screensaver-command -q
Screensaver is not active (rough translation)
Screensaver is not inhibited (rough translation)

And then, if I re-run the program after simply starting EoG:

jeff@kusanagi:~$ gnome-screensaver-command -q

** (gnome-screensaver-command:10645): WARNING **: org.freedesktop.DBus.Error.UnknownMethod raised:
 Method "GetActive" with signature "" on interface "org.gnome.ScreenSaver" doesn't exist

jeff@kusanagi:~$ killall gnome-screensaver (and I restart it with alt-f2)
jeff@kusanagi:~$ gnome-screensaver-command -q
Screensaver is not active (rough translation)

** (gnome-screensaver-command:10739): WARNING **: org.freedesktop.DBus.Error.UnknownMethod raised:
 Method "GetInhibitors" with signature "" on interface "org.gnome.ScreenSaver" doesn't exist

** Message: Did not receive a reply from screensaver.

...and so on.