Failed to connect to socket /var/run/dbus/system_bus_socket

Hello, I installed a big update that appeared on Saturday (I believe it was 11.10, I did not really pay attention as I was not expecting problems… Sorry), and my computer never started again. There is a message “Your current screen, graphic card, and input device settings could not be detected correctly. You will need to configure these manually.” However the next screen does not allow me to configure anything and Ubuntu does not start at all. I only have access to the console but I don’t know how to solve it from there.
During the start up, the following line appears:
“unable to connect to system bus: Failed to connect to socket /var/run/dbus/system_bus_socket: Connection refused”

The following start-up error is showed:

X.org X server 1.10.1
Release date: 2011-04-15
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-29-server i686 Ubuntu
Current Operating System: Linux Petya-inspiron-1420 2.6.38-11-generic #50-Ubuntu SMP
Mon Sep 12 21:18:14 UTC 2011 i686
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-2.6.38-11-generic root=UUID=42bc2a9a-2c14-4d9f-94ce-dcaf13f43743 ro quiet splash vt.handoff=7
Build date: 11 august 2011 03:47:56 PM
Xorg-server 2:1.10.1-1ubuntu1.2 (For technical support please see https://www.ubuntu.com/support)
Current version of pixman: 0.22.2
   Before reporting problems, check wiki.x.org to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) information, (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: “/var/log/Xorg.0.log”, Time: Sun Oct 16 07:52:59 2011
(==) Using config file: “/etc/X11/xorg.config”

Can you please help?
Is it possible to uninstall that last update?