No me deja actualizar mi ubuntu a 14.04

[jostin]

Ubuntu no me deja actualizar de 12.04 al 14.04 no entiendo porque!

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.17
ProcVersionSignature: Ubuntu 3.2.0-67.101-generic 3.2.60
Uname: Linux 3.2.0-67-generic i686
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: i386
Date: Tue Aug 19 20:48:18 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1408499007
 com.ubuntu.update-manager window-height 776
 com.ubuntu.update-manager window-width 1215
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=es_CO.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-08-20 (0 days ago)
VarLogDistupgradeTermlog:

[Mário Jorge Simões Nunes (as1534852)]

Ubuntu não me deixa actualizar de 13.10 para 14.04 e não entendo porquê!