package mpd 0.15.4-1ubuntu3 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

Binary package hint: mpd

mpd package fail at adding user to audio grp

heres the install script dbg :
Need to get 0B/179kB of archives.
After this operation, 520kB of additional disk space will be used.
Selecting previously deselected package mpd.
(Reading database ... 172349 files and directories currently installed.)
Unpacking mpd (from .../mpd_0.15.4-1ubuntu3_i386.deb) ...
Processing triggers for ureadahead ...
Processing triggers for man-db ...
Setting up mpd (0.15.4-1ubuntu3) ...
useradd: cannot lock /etc/gshadow; try again later.
adduser: `/usr/sbin/useradd -d /var/lib/mpd -g audio -s /bin/false -u 125 mpd' returned error code 10. Exiting.
dpkg: error processing mpd (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 mpd
E: Sub-process /usr/bin/dpkg returned an error code (1)
blackmatter@blacknet:~$

tnx in advance

ProblemType: Package
DistroRelease: Ubuntu 10.04
Package: mpd 0.15.4-1ubuntu3
ProcVersionSignature: Ubuntu 2.6.32-24.42-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Thu Sep 16 13:26:33 2010
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release i386 (20100816.1)
SourcePackage: mpd
Title: package mpd 0.15.4-1ubuntu3 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1