sudo do-release-upgrade - unresolvable problem

[Vito Macchia]

Distributor ID: Ubuntu
Description: Ubuntu 13.10
Release: 13.10
Codename: saucy
KDE desktop/Kubuntu

sudo do-release-upgrade

yelds to

An unresolvable problem occurred while calculating the upgrade.

from Kubuntu 13.10 saucy to 14.04 roary. No more information showed.

ubuntu-bug ubuntu-release-upgrader-core
crashes KCrash

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 i686
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: i386
CrashDB: ubuntu
Date: Fri Apr 18 10:17:50 2014
InstallationDate: Installed on 2014-01-08 (99 days ago)
InstallationMedia: Kubuntu 13.10 "Saucy Salamander" - Release i386 (20131016.1)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to saucy on 2014-04-18 (0 days ago)