Ubuntu Upgrade from 12.04 to 14.04.1

[Sivam]

I tried to Upgrade Ubuntu from 12.04 to 14.04.1. However, it kept failing and saying that an unresolved error occured.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.17
ProcVersionSignature: Ubuntu 3.2.0-69.103-generic 3.2.62
Uname: Linux 3.2.0-69-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu17.7
Architecture: amd64
Date: Thu Sep 25 23:51:33 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1411685400
 com.ubuntu.update-manager show-details true
 com.ubuntu.update-manager window-height 658
 com.ubuntu.update-manager window-width 600
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-09-25 (0 days ago)
VarLogDistupgradeTermlog:

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.