Bug#751736: gnome-screensaver: quite often unable to unlock the screen

[Janusz S. Bień]

Package: gnome-screensaver
Version: 3.6.1-1
Severity: important

Quite often I'm unable to unlock the screen. This happens almost always
when the computer is not used locally for serveral hours.

The screen look similar to 

    http://i.stack.imgur.com/ejs4C.png

After pressing Enter the arrows moves but that's all.

I tried the unlock the screen remotely following the advice of

  http://askubuntu.com/questions/341014/unlock-login-screen-using-command-line

but it doesn't work for me:

jsbien at debian2050pc1:~$ DISPLAY=:0 gnome-screensaver-command -d
** Message: Failed to get session bus: Error spawning command line 'dbus-launch --autolaunch=c5dd83e04d31e5407fe1366551d54718 --binary-syntax --close-stderr': Child process exited with code 1


jsbien at debian2050pc1:~$ export DISPLAY=:0
jsbien at debian2050pc1:~$ dbus-send --session \
>          --dest=org.gnome.ScreenSaver \
>          --type=method_call \
>          --print-reply \
>          --reply-timeout=20000 \
>          /org/gnome/ScreenSaver \
>          org.gnome.ScreenSaver.SetActive \
>          boolean:false
Failed to open connection to "session" message bus: /usr/bin/dbus-launch terminated abnormally with the following error: No protocol specified
Autolaunch error: X11 initialization failed.

I will appreciate your help.

Best regards

Janusz

-- System Information:
Debian Release: jessie/sid
  APT prefers testing-updates
  APT policy: (500, 'testing-updates'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.13-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages gnome-screensaver depends on:
ii  dbus-x11                   1.8.2-1
ii  gnome-icon-theme           3.12.0-1
ii  gnome-session-bin          3.8.4-4
ii  gsettings-desktop-schemas  3.8.2-2
ii  libc6                      2.18-7
ii  libcairo2                  1.12.16-2
ii  libdbus-1-3                1.8.2-1
ii  libdbus-glib-1-2           0.102-1
ii  libgdk-pixbuf2.0-0         2.30.7-1
ii  libglib2.0-0               2.40.0-3
ii  libgnome-desktop-3-7       3.8.4-2
ii  libgnomekbd8               3.6.0-1
ii  libgtk-3-0                 3.12.2-1
ii  libpam0g                   1.1.8-3
ii  libx11-6                   2:1.6.2-2
ii  libxext6                   2:1.3.2-1
ii  libxklavier16              5.2.1-1
ii  libxxf86vm1                1:1.1.3-1

Versions of packages gnome-screensaver recommends:
ii  gnome-power-manager   3.8.2-1
ii  libpam-gnome-keyring  3.8.2-2+b1

gnome-screensaver suggests no packages.

-- no debconf information