I have upgrade my ubuntu from 11.10 to 12.04. at last i can found that when i tries to install some packages it shows a error.
after reading some blog i tried to fix that error by "sudo dpkg --configure -a". but when i run this command it show another error this

Setting up colord (0.1.16-2) ...

useradd: cannot lock /etc/passwd; try again later.

adduser: `/usr/sbin/useradd -d /var/lib/colord -g colord -s /bin/false -u 115 colord' returned error code 1. Exiting.

dpkg: error processing colord (--configure):

 subprocess installed post-installation script returned error exit status 1

Setting up whoopsie (0.1.32) ...

useradd: cannot lock /etc/passwd; try again later.

adduser: `/usr/sbin/useradd -d /nonexistent -g whoopsie -s /bin/false -u 115 whoopsie' returned error code 1. Exiting.

dpkg: error processing whoopsie (--configure):

 subprocess installed post-installation script returned error exit status 1

Setting up lightdm (1.2.1-0ubuntu1) ...

Adding system user `lightdm' (UID 115) ...

Adding new user `lightdm' (UID 115) with group `lightdm' ...

useradd: cannot lock /etc/passwd; try again later.

adduser: `/usr/sbin/useradd -d /var/lib/lightdm -g lightdm -s /bin/false -u 115 lightdm' returned error code 1. Exiting.

dpkg: error processing lightdm (--configure):

 subprocess installed post-installation script returned error exit status 1

dpkg: dependency problems prevent configuration of ubuntu-desktop:

 ubuntu-desktop depends on lightdm; however:

  Package lightdm is not configured yet.

dpkg: error processing ubuntu-desktop (--configure):

 dependency problems - leaving unconfigured

Errors were encountered while processing:

 colord

 whoopsie

 lightdm

 ubuntu-desktop

what can i do now ?