gnome-screensaver crashes after long idle

After locking the computer for a long time ~1h the screensaver becomes unresponsive (unable to log back in)

in VT I could do:
killall gnome-screensaver to return to the desktop.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: gnome-screensaver 3.4.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-27.43-generic 3.2.21
Uname: Linux 3.2.0-27-generic x86_64
ApportVersion: 2.0.1-0ubuntu12
Architecture: amd64
Date: Thu Aug 9 16:07:57 2012
EcryptfsInUse: Yes
GnomeSessionIdleInhibited: No
GnomeSessionInhibitors: None
GsettingsGnomeSession:
 org.gnome.desktop.session idle-delay uint32 600
 org.gnome.desktop.session session-name 'ubuntu'
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-screensaver
UpgradeStatus: No upgrade log present (probably fresh install)
WindowManager: No value set for `/desktop/gnome/session/required_components/windowmanager'