package passwd 1:4.1.4.2+svn3283-3ubuntu5 failed to install/upgrade: package passwd is not ready for configuration cannot configure (current status `half-installed')

i dont know

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: passwd 1:4.1.4.2+svn3283-3ubuntu5.1
ProcVersionSignature: Ubuntu 3.0.0-18.31-generic 3.0.26
Uname: Linux 3.0.0-18-generic i686
ApportVersion: 2.0.1-0ubuntu12
Architecture: i386
Date: Thu Sep 13 08:37:25 2012
DuplicateSignature:
 Unpacking replacement passwd ...
 dpkg: unrecoverable fatal error, aborting:
  fork failed: Cannot allocate memory
 dpkg: error processing passwd (--configure):
  package passwd is not ready for configuration
ErrorMessage: package passwd is not ready for configuration cannot configure (current status `half-installed')
SourcePackage: shadow
Title: package passwd 1:4.1.4.2+svn3283-3ubuntu5 failed to install/upgrade: package passwd is not ready for configuration cannot configure (current status `half-installed')
UpgradeStatus: Upgraded to precise on 2012-05-05 (134 days ago)