This also happens to me on all machines that I use. This machine is a Dell E6510 with a Core i7 620M, kernel 3.8-rc4, ubuntu 12.04-based distribution using gnome-shell, using NVIDIA graphics, version 310.32. During this morning's update, this is the related part of my .xsession-errors file:

06:13:37.787 DEBUG MainWindow:1122                  position 60 scrobble point 125 status 0 
06:13:47.788 DEBUG MainWindow:1122                  position 70 scrobble point 125 status 0 
06:13:57.787 DEBUG MainWindow:1122                  position 80 scrobble point 125 status 0 
06:14:07.787 DEBUG MainWindow:1122                  position 90 scrobble point 125 status 0 
06:14:17.787 DEBUG MainWindow:1122                  position 100 scrobble point 125 status 0 
06:14:27.787 DEBUG MainWindow:1122                  position 110 scrobble point 125 status 0 
[Fatal 06:14:34.017] [GLib-GObject] g_object_ref: assertion `G_IS_OBJECT (object)' failed
Stacktrace:


Native stacktrace:

06:14:37.787 DEBUG MainWindow:1122                  position 120 scrobble point 125 status 0 
[Info  06:14:40.646] Docky version: 2.1.4 Release
[Info  06:14:40.663] Kernel version: 3.8.0.43
[Info  06:14:40.664] CLR version: 4.0.30319.1
[Info  06:14:41.100] [ThemeService] Setting theme: LuninuXOS
[Warn  06:14:41.121] [DesktopItemService] Could not find remap file '/home/ray/.local/share/docky/remaps.ini'!
[Info  06:14:41.370] [DockServices] Dock services initialized.
[Info  06:14:42.019] [PluginManager] Loaded "Trash".
Window manager warning: Log level 8: _shell_embedded_window_unrealize: assertion `SHELL_IS_EMBEDDED_WINDOW (window)' failed
[Info  06:14:43.106] [Helper] Starting banshee_control.py
[Info  06:14:43.125] [Helper] Starting liferea_badge.py
[Info  06:14:43.130] [Helper] Starting mpd_control.py
[Info  06:14:43.134] [Helper] Starting open_terminal_here.py
[Info  06:14:43.141] [Helper] Starting skype_control.py
[Info  06:14:43.165] [HelperService] Helper added: /usr/share/dockmanager/scripts/banshee_control.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/deluge_badge.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/emesene_control.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/gajim_badge.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/gtg_menus.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/liferea_badge.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/mpd_control.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/open_terminal_here.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/pidgin_control.py
[Info  06:14:43.173] [HelperService] Helper added: /usr/share/dockmanager/scripts/pithos_control.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/rhythmbox_control.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/skype_control.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/tomboy_menus.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/transmission_badge.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/tsclient_menus.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/workrave_helper.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/zeitgeist_journal.py
[Info  06:14:43.174] [HelperService] Helper added: /usr/share/dockmanager/scripts/zeitgeist_menus.py
[Info  06:14:43.190] [Helper] liferea_badge.py :: No module named dockmanager.dockmanager
[Info  06:14:43.295] [Helper] banshee_control.py :: No module named dockmanager.dockmanager
[Error 06:14:43.303] [Helper] mpd_control.py :: mpd-control: python-dockmanager is needed
[Info  06:14:43.327] [Helper] banshee_control.py has exited (Code 0).
[Info  06:14:43.331] [Helper] liferea_badge.py has exited (Code 0).
[Info  06:14:43.334] [Helper] mpd_control.py has exited (Code 0).
[Info  06:14:43.337] [Helper] open_terminal_here.py has exited (Code 0).
[Info  06:14:43.340] [Helper] skype_control.py has exited (Code 0).
[Warn  06:14:43.364] [DrawingService] Error loading icon from file '/usr/share/pithos/media/icon.svg': Failed to open file '/usr/share/pithos/media/icon.svg': No such file or directory
[Info  06:14:43.366] [DrawingService] Could not find '/usr/share/pithos/media/icon.svg', using fallback of 'extension'.
[Warn  06:14:43.459] [DrawingService] Error loading icon from file '/usr/share/pixmaps/workrave/workrave.xpm': Failed to open file '/usr/share/pixmaps/workrave/workrave.xpm': No such file or directory
[Info  06:14:43.462] [DrawingService] Could not find '/usr/share/pixmaps/workrave/workrave.xpm', using fallback of 'extension'.
Window manager warning: Log level 8: meta_window_raise: assertion `!window->override_redirect' failed
Window manager warning: Log level 8: meta_window_lower: assertion `!window->override_redirect' failed
06:14:47.787 DEBUG MainWindow:1122                  position 130 scrobble point 125 status 0