Trying to upgrade from 13.04 to 13.10

[Alan Hamilton]

Upgrade process stops with: Could not determine 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.

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 x86_64
ApportVersion: 2.9.2-0ubuntu8.5
Architecture: amd64
CrashDB: ubuntu
Date: Wed Mar 19 22:00:32 2014
InstallationDate: Installed on 2014-03-18 (1 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to raring on 2014-03-19 (0 days ago)
VarLogDistupgradeTermlog: