Just got bit by this one again, clean lucid install.  The fix is to "rm -f /etc/gshadow.lock". 

"sudo do-release-upgrade" finishes with this: 


The upgrade has aborted. Your system could be in an unusable state. A 
recovery will run now (dpkg --configure -a). 

Setting up dbus (1.4.18-1ubuntu1) ...
groupadd: cannot lock /etc/gshadow; try again later.
adduser: `/usr/sbin/groupadd -g 112 messagebus' returned error code 10. Exiting.
dpkg: error processing dbus (--configure):
 subprocess installed post-installation script returned error exit status 1
Setting up whoopsie (0.1.32) ...
groupadd: cannot lock /etc/gshadow; try again later.
adduser: `/usr/sbin/groupadd -g 112 whoopsie' returned error code 10. Exiting.
dpkg: error processing whoopsie (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of language-selector-common:
 language-selector-common depends on dbus; however:
  Package dbus is not configured yet.
dpkg: error processing language-selector-common (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of ubuntu-standard:
 ubuntu-standard depends on language-selector-common; however:
  Package language-selector-common is not configured yet.
dpkg: error processing ubuntu-standard (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of accountsservice:
 accountsservice depends on dbus; however:
  Package dbus is not configured yet.
dpkg: error processing accountsservice (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 dbus
 whoopsie
 language-selector-common
 ubuntu-standard
 accountsservice

Upgrade complete 

The upgrade has completed but there were errors during the upgrade 
process. 

To continue please press [ENTER]

-------------- 

...'x' to get out of it, then: 

root@asdf:~# cd /etc
root@asdf:/etc# ls -l *lock
ls: unrecognized prefix: hl
ls: unparsable value for LS_COLORS environment variable
-rw------- 1 root root 0 Aug 14 16:41 gshadow.lock
root@asdf:/etc# lsof gshadow.lock
root@asdf:/etc# rm -f gshadow.lock
root@asdf:/etc# apt-get dist-upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
5 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? 
Setting up dbus (1.4.18-1ubuntu1) ...
dbus start/running, process 4465
Setting up accountsservice (0.6.15-2ubuntu9.3) ...
Setting up language-selector-common (0.79) ...
Installing new version of config file /etc/fonts/conf.avail/69-language-selector-zh-tw.conf ...
Installing new version of config file /etc/fonts/conf.avail/69-language-selector-ja-jp.conf ...
Installing new version of config file /etc/fonts/conf.avail/30-cjk-aliases.conf ...
Removing obsolete conffile /etc/fonts/conf.avail/69-language-selector-ko-kr.conf ...
Removing obsolete conffile /etc/fonts/conf.avail/29-language-selector-ko-kr.conf ...
Setting up whoopsie (0.1.32) ...
whoopsie start/running, process 4562
Setting up ubuntu-standard (1.267) ...
root@asdf:/etc# 

...I've replicated this three times in a row now on kvm guests,happy to run any commands on this side and post results here if that would be useful.