Bug#759745: more info

[Peter Ralph]

The same thing happened to me, and installing systemd-sysv also fixed
the problem.  I am adding more info to help others find it.  (also
appears, perhaps: https://bbs.archlinux.org/viewtopic.php?id=183923 )

Here are the first set of ominous errors from :0-greeter.log that
might be related:
"
Gjs-Message: JS LOG: Failed to register
AuthenticationAgent(gnome-shell:2561): Gjs-WARNING **: JS ERROR:
Exception in callback for signal: startup-prepared: Gio.DBusError:
GDBus.Error:org.freedesktop.DBus.Error.AccessDenied: No session
available
LoginDialog<._init at resource:///org/gnome/shell/gdm/loginDialog.js:376
wrapper at resource:///org/gnome/gjs/modules/lang.js:169
_Base.prototype._construct at resource:///org/gnome/gjs/modules/lang.js:110
Class.prototype._construct/newClass at resource:///org/gnome/gjs/modules/lang.js:204
ScreenShield<._ensureUnlockDialog at resource:///org/gnome/shell/ui/screenShield.js:973
wrapper at resource:///org/gnome/gjs/modules/lang.js:169
ScreenShield<.showDialog at resource:///org/gnome/shell/ui/screenShield.js:919
wrapper at resource:///org/gnome/gjs/modules/lang.js:169
_initializeUI/<@resource:///org/gnome/shell/ui/main.js:208
_emit at resource:///org/gnome/gjs/modules/signals.js:124
LayoutManager<._prepareStartupAnimation at resource:///org/gnome/shell/ui/layout.js:623
wrapper at resource:///org/gnome/gjs/modules/lang.js:169
LayoutManager<._loadBackground/signalId<@resource:///org/gnome/shell/ui/layout.js:568
_emit at resource:///org/gnome/gjs/modules/signals.js:124
SystemBackground<._init/<.onFinished<@resource:///org/gnome/shell/ui/background.js:650
BackgroundCache<._loadImageContent/<@resource:///org/gnome/shell/ui/background.js:208
"

Also see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747821
(systemd-shim) -- at least, I experienced these symptoms
simultaneously.

-p