Comment 56 for bug 856810

I encountered this bug when upgrading from Ubuntu 11.04 to 11.10. I read all the comments from this issue and the accompanying issue mentioned previously, then I resolved this issue by doing the following actions (in this order):

sudo dpkg-reconfigure lightdm
sudo apt-get purge gdm
sudo rm /var/var/dbus/pid
su root
created directories /run and /run/lock (these already existed)
moved contents of /var/run into /run and /var/lock into /run/lock,
delete directories /var/run and /var/lock
create replacement simlinks; e.g. 'ln -s /run /var/run' and 'ln -s /run/lock /var/lock'
reboot

I rebooted twice just to be sure since I went through part of this process once, resolved it, then the problem reappeared after reboot. The problem only stayed resolved after doing ALL of the above steps. Had I been an uneducated user (not a techie) I would have been really angry. Ubuntu community needs to upgrade the OS soon to fix this. This is a huge issue since the machine UI was unusable until this fix was in place!