package postgresql-8.4 8.4.16-0ubuntu12.04 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 1

[Murali Adari]

I am trying to uninstall postgrsql along with its other dependedent packages by running the following command:
sudo apt-get --purge remove postgresql-8.4 postgresql-client-8.4 postgresql-client-common postgresql-common

But get the below error:
Reading state information... Done
The following packages will be REMOVED:
  postgresql-8.4* postgresql-client-8.4* postgresql-client-common* postgresql-common*
0 upgraded, 0 newly installed, 4 to remove and 0 not upgraded.
3 not fully installed or removed.
After this operation, 20.8 MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 270860 files and directories currently installed.)
Removing postgresql-8.4 ...
/var/lib/dpkg/info/postgresql-8.4.prerm: line 7: /usr/share/postgresql-common/maintscripts-functions: No such file or directory
dpkg: error processing postgresql-8.4 (--purge):
 subprocess installed pre-removal script returned error exit status 1
Removing postgresql-client-common ...
Purging configuration files for postgresql-client-common ...
dpkg: postgresql-common: dependency problems, but removing anyway as you requested:
 postgresql-8.4 depends on postgresql-common (>= 129~); however:
  Package postgresql-common is to be removed.
Removing postgresql-common ...
 * Stopping PostgreSQL 8.4 database server [ OK ]
Removing 'diversion of /usr/bin/pg_config to /usr/bin/pg_config.libpq-dev by postgresql-common'
Purging configuration files for postgresql-common ...
dpkg: warning: while removing postgresql-common, directory '/var/lib/postgresql' not empty so not removed.
dpkg: postgresql-client-8.4: dependency problems, but removing anyway as you requested:
 postgresql-8.4 depends on postgresql-client-8.4; however:
  Package postgresql-client-8.4 is to be removed.
Removing postgresql-client-8.4 ...
/var/lib/dpkg/info/postgresql-client-8.4.prerm: line 8: /usr/share/postgresql-common/maintscripts-functions: No such file or directory
dpkg: error processing postgresql-client-8.4 (--purge):
 subprocess installed pre-removal script returned error exit status 1
/var/lib/dpkg/info/postgresql-client-8.4.postinst: line 5: /usr/share/postgresql-common/maintscripts-functions: No such file or directory
dpkg: error while cleaning up:
 subprocess installed post-installation script returned error exit status 1
Processing triggers for man-db ...
Processing triggers for ureadahead ...
ureadahead will be reprofiled on next reboot
Errors were encountered while processing:
 postgresql-8.4
 postgresql-client-8.4
E: Sub-process /usr/bin/dpkg returned an error code (1)

I have a bunch of postgreSQL updates showing up in the update manager , however when I click on Install Updates, the Update Manager also fails. So here I am stuck unable to update or uninstall.

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: postgresql-8.4 8.4.16-0ubuntu12.04
ProcVersionSignature: Ubuntu 3.5.0-41.64~precise1-generic 3.5.7.21
Uname: Linux 3.5.0-41-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.5
AptOrdering:
 postgresql-8.4: Purge
 postgresql-client-8.4: Purge
 postgresql-common: Purge
 postgresql-client-common: Purge
 hbase: Configure
Architecture: amd64
Date: Sun Oct 20 19:38:08 2013
DpkgTerminalLog:
 Removing postgresql-8.4 ...
 /var/lib/dpkg/info/postgresql-8.4.prerm: line 7: /usr/share/postgresql-common/maintscripts-functions: No such file or directory
 dpkg: error processing postgresql-8.4 (--purge):
  subprocess installed pre-removal script returned error exit status 1
DuplicateSignature: package:postgresql-8.4:8.4.16-0ubuntu12.04:subprocess installed pre-removal script returned error exit status 1
ErrorMessage: subprocess installed pre-removal script returned error exit status 1
InstallationMedia: Ubuntu 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130214)
MarkForUpload: True
SourcePackage: postgresql-8.4
Title: package postgresql-8.4 8.4.16-0ubuntu12.04 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)