OLD issue still can not upgrade from 13.04 to 13.1

[Tushar Gujrathi]

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

THIS MESSAGE ENDS MY EFFORTS TO UPGRADE...WHAT TO DO..?????

System-Product-Name:~$ lsb_release -rd
Description: Ubuntu 13.04
Release: 13.04
System-Product-Name:~$ apt-cache policy pkgname
N: Unable to locate package pkgname

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: ubuntu-release-upgrader-core 1:0.192.13
ProcVersionSignature: Ubuntu 3.8.0-35.50-generic 3.8.13.13
Uname: Linux 3.8.0-35-generic i686
ApportVersion: 2.9.2-0ubuntu8.5
Architecture: i386
CrashDB: ubuntu
Date: Thu Jan 16 21:23:00 2014
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to raring on 2014-01-16 (0 days ago)
VarLogDistupgradeTermlog: