Comment 6 for bug 273748

Had it here too, but re-running apt-get install libvirt-bin fixed it
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)
nathan@jaguar:~$ sudo apt-get install libvirt-bin
Reading package lists... Done
Building dependency tree
Reading state information... Done
libvirt-bin is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0B of additional disk space will be used.
Setting up libvirt-bin (0.4.4-3ubuntu3.1) ...
addgroup: The group `libvirtd' already exists as a system group. Exiting.
 * Starting libvirt management daemon libvirtd [ OK ]