package icedtea-6-plugin (not installed) failed to install/upgrade: conflicting packages - not installing icedtea-6-plugin

[Swamy Gali]

The Ubuntu Software Centre is not getting updated.....and packages like vlc, kmplayer etc...not getting installed through command sudo apt-get install package in terminal....
I want to know solution for this problem.......

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: icedtea-6-plugin (not installed)
ProcVersionSignature: Ubuntu 3.2.0-29.46-generic-pae 3.2.24
Uname: Linux 3.2.0-29-generic-pae i686
ApportVersion: 2.0.1-0ubuntu12
Architecture: i386
Date: Wed Apr 3 05:42:01 2013
DpkgTerminalLog:
 dpkg: regarding .../icedtea-6-plugin_1.2-2ubuntu1.3_i386.deb containing icedtea-6-plugin:
  icedtea-6-plugin conflicts with icedtea6-plugin (<< 6b21.2~pre1-1~)
   icedtea6-plugin (version 6b20-1.9.13-0ubuntu1~10.04.1) is present and unpacked but not configured.
 dpkg: error processing /var/cache/apt/archives/icedtea-6-plugin_1.2-2ubuntu1.3_i386.deb (--unpack):
  conflicting packages - not installing icedtea-6-plugin
ErrorMessage: conflicting packages - not installing icedtea-6-plugin
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release i386 (20120817.3)
SourcePackage: icedtea-web
Title: package icedtea-6-plugin (not installed) failed to install/upgrade: conflicting packages - not installing icedtea-6-plugin
UpgradeStatus: No upgrade log present (probably fresh install)