Ubuntu – Couldn’t connect to accessibility bus

That's a very weird file path //bin/dbus-launch - that should've been /usr/bin/dbus-launch. Does the system hang there or does it allow you to go further?

Have you tried searching for that path in your home? This will go through your files/documents in home and echo the filename that contains "dbus-launch":

grep -ri dbus-launch /home/myusername

Also try creating a new user.

• Press CTRL+ALT+F1 - this will get you in the console. Login with your credentials.

• Execute:

   sudo adduser mynewuser
   sudo adduser mynewuser admin
  

  It will ask for a password twice, type it in. You can leave the rest of the fields empty (full name etc.), just press enter. The second command will add you as administrator.

• Now restart your lightdm (desktop manager): sudo service lightdm restart

If the new user works, then it's definitely a problem in your home folder (probably hidden folder settings, press ctrl+H in nautilus to show hidden files/folders).

SirCharlo's answer worked for me. Same problem on ubuntu 12.04 (precise pangolin). Yeah, I use su (root) also. Shame, shame. Same problem starting emacs too.

The problem seems to be that DBUS_SESSION_BUS_ADDRESS retains its value when you su instead of picking up the value in /root/.dbus/session-bus/

from man dbus-launch:

   ...
   The second common reason for autolaunch is an su to another  user,  and
   display  of  X  applications  running as the second user on the display
   belonging to the first user. Perhaps the ideal fix in this  case  would
   be  to allow the second user to connect to the session bus of the first
   user, just as they can connect to the first user's display.  However, a
   mechanism for that has not been coded.
   ...

Use sudo, suedit, gksu.

Or if you MUST use su, then try adding this to your /root/.bashrc:

sessionfile=`find "${HOME}/.dbus/session-bus/" -maxdepth 1 -type f`
if [ -f "$sessionfile" ] ; then
    if grep -q "^DBUS_SESSION_BUS_ADDRESS=" "${sessionfile}" ; then
        export `grep "^DBUS_SESSION_BUS_ADDRESS=" "${sessionfile}"`
    else
        echo "DBUS_SESSION_BUS_ADDRESS not found in ${sessionfile}"
    fi
else
    echo "no session address file found in ${HOME}/.dbus/session-bus"
fi