dist-upgrade fails from 13.10 to 14.04

[Alec MacLean]

Performing the Distribution Upgrade (using GUI tools), after "calculating changes", the system reports error of:

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

Previous upgrades (12.10 -> 13.04 -> 13.10) on the same hardware have performed well.
I'm not knowledgable enough to determine what may be the cause of the failure on this upgrade.

Only significant difference since last upgrade is that I've added the Cinnamon 2.0 desktop.
I have tried re-running the upgrade while using Unity (my thinking being in case the upgrad needed to be able to disable the Cinnamon packages), but the same error occurs under Unity.

I have submitted this as suggested by the error dialog itself, initiated from Terminal using the provided "ubuntu-bug ubuntu-release-upgrader-core" command.

Requested additional information:
Release: 13.10
Package is the Distribution Upgrade from Saucy to Trusty
I expected the upgrade to proceed.
What happened is detailed above.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubuntu-release-upgrader-core 1:0.205.5
ProcVersionSignature: Ubuntu 3.11.0-19.33-generic 3.11.10.5
Uname: Linux 3.11.0-19-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
CrashDB: ubuntu
Date: Sat Apr 19 22:36:27 2014
InstallationDate: Installed on 2013-04-27 (357 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to saucy on 2014-04-19 (0 days ago)
VarLogDistupgradeTermlog: