I ran "sudo do-release-upgrade". It fails with a note saying why it might be failing and listing three reasons, none of which apply. In the case that none apply, it requests I file a bug. Here's output:
$ sudo do-release-upgrade
Reading cache
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Ign http://security.ubuntu.com trusty-security InRelease
Ign http://fr.archive.ubuntu.com trusty InRelease
Hit http://security.ubuntu.com trusty-security Release.gpg
Ign http://fr.archive.ubuntu.com trusty-updates InRelease
Hit http://fr.archive.ubuntu.com trusty Release.gpg
Hit http://security.ubuntu.com trusty-security Release
Hit http://fr.archive.ubuntu.com trusty-updates Release.gpg
Hit http://security.ubuntu.com trusty-security/main Sources
Hit http://fr.archive.ubuntu.com trusty Release
Hit http://security.ubuntu.com trusty-security/restricted Sources
Hit http://fr.archive.ubuntu.com trusty-updates Release
Hit http://security.ubuntu.com trusty-security/universe Sources
Hit http://fr.archive.ubuntu.com trusty/main Sources
Hit http://security.ubuntu.com trusty-security/multiverse Sources
Hit http://fr.archive.ubuntu.com trusty/restricted Sources
Hit http://security.ubuntu.com trusty-security/main i386 Packages
Hit http://fr.archive.ubuntu.com trusty/universe Sources
Hit http://security.ubuntu.com trusty-security/restricted i386 Packages
Hit http://fr.archive.ubuntu.com trusty/multiverse Sources
Hit http://security.ubuntu.com trusty-security/universe i386 Packages
Hit http://fr.archive.ubuntu.com trusty/main i386 Packages
Hit http://security.ubuntu.com trusty-security/multiverse i386 Packages
Hit http://fr.archive.ubuntu.com trusty/restricted i386 Packages
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://fr.archive.ubuntu.com trusty/universe i386 Packages
Hit http://security.ubuntu.com trusty-security/multiverse Translation-en
Hit http://fr.archive.ubuntu.com trusty/multiverse i386 Packages
Hit http://security.ubuntu.com trusty-security/restricted Translation-en
Err http://fr.archive.ubuntu.com trusty/main Translation-en_US
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Hit http://fr.archive.ubuntu.com trusty/main Translation-en
Err http://fr.archive.ubuntu.com trusty/multiverse Translation-en_US
Hit http://fr.archive.ubuntu.com trusty/multiverse Translation-en
Err http://fr.archive.ubuntu.com trusty/restricted Translation-en_US
Hit http://fr.archive.ubuntu.com trusty/restricted Translation-en
Err http://fr.archive.ubuntu.com trusty/universe Translation-en_US
Hit http://fr.archive.ubuntu.com trusty/universe Translation-en
Hit http://fr.archive.ubuntu.com trusty-updates/main Sources
Hit http://fr.archive.ubuntu.com trusty-updates/restricted Sources
Hit http://fr.archive.ubuntu.com trusty-updates/universe Sources
Hit http://fr.archive.ubuntu.com trusty-updates/multiverse Sources
Hit http://fr.archive.ubuntu.com trusty-updates/main i386 Packages
Hit http://fr.archive.ubuntu.com trusty-updates/restricted i386 Packages
Hit http://fr.archive.ubuntu.com trusty-updates/universe i386 Packages
Hit http://fr.archive.ubuntu.com trusty-updates/multiverse i386 Packages
Hit http://fr.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://fr.archive.ubuntu.com trusty-updates/multiverse Translation-en
Hit http://fr.archive.ubuntu.com trusty-updates/restricted Translation-en
Hit http://fr.archive.ubuntu.com trusty-updates/universe Translation-en
Err http://fr.archive.ubuntu.com trusty/main Translation-en_US
Err http://fr.archive.ubuntu.com trusty/multiverse Translation-en_US
Err http://fr.archive.ubuntu.com trusty/restricted Translation-en_US
Err http://fr.archive.ubuntu.com trusty/universe Translation-en_US
Err http://fr.archive.ubuntu.com trusty/main Translation-en_US
Err http://fr.archive.ubuntu.com trusty/multiverse Translation-en_US
Err http://fr.archive.ubuntu.com trusty/restricted Translation-en_US
Err http://fr.archive.ubuntu.com trusty/universe Translation-en_US
Err http://fr.archive.ubuntu.com trusty/main Translation-en_US
Err http://fr.archive.ubuntu.com trusty/multiverse Translation-en_US
Err http://fr.archive.ubuntu.com trusty/restricted Translation-en_US
Err http://fr.archive.ubuntu.com trusty/universe Translation-en_US
Ign http://fr.archive.ubuntu.com trusty/main Translation-en_US
Ign http://fr.archive.ubuntu.com trusty/multiverse Translation-en_US
Ign http://fr.archive.ubuntu.com trusty/restricted Translation-en_US
Ign http://fr.archive.ubuntu.com trusty/universe Translation-en_US
Fetched 0 B in 6s (5,901 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Updating repository information
Ign http://fr.archive.ubuntu.com utopic InRelease
Ign http://fr.archive.ubuntu.com utopic-updates InRelease
Get:1 http://fr.archive.ubuntu.com utopic Release.gpg [933 B]
Get:2 http://fr.archive.ubuntu.com utopic-updates Release.gpg [933 B]
Ign http://security.ubuntu.com utopic-security InRelease
Get:3 http://fr.archive.ubuntu.com utopic Release [112 kB]
Get:4 http://security.ubuntu.com utopic-security Release.gpg [933 B]
Get:5 http://security.ubuntu.com utopic-security Release [59.7 kB]
Get:6 http://fr.archive.ubuntu.com utopic-updates Release [59.7 kB]
Get:7 http://fr.archive.ubuntu.com utopic/main Sources [1,046 kB]
Get:8 http://security.ubuntu.com utopic-security/main Sources [7,232 B]
Get:9 http://security.ubuntu.com utopic-security/restricted Sources [14 B]
Get:10 http://security.ubuntu.com utopic-security/universe Sources [14 B]
Get:11 http://security.ubuntu.com utopic-security/multiverse Sources [14 B]
Get:12 http://security.ubuntu.com utopic-security/main i386 Packages [14.6 kB]
Get:13 http://security.ubuntu.com utopic-security/restricted i386 Packages [14 B]
Get:14 http://security.ubuntu.com utopic-security/universe i386 Packages [2,652 B]
Get:15 http://security.ubuntu.com utopic-security/multiverse i386 Packages [14 B]
Get:16 http://security.ubuntu.com utopic-security/main Translation-en [10.0 kB]
Get:17 http://security.ubuntu.com utopic-security/multiverse Translation-en [14 B]
Get:18 http://security.ubuntu.com utopic-security/restricted Translation-en [14 B]
Get:19 http://security.ubuntu.com utopic-security/universe Translation-en [2,065 B]
Get:20 http://fr.archive.ubuntu.com utopic/restricted Sources [5,115 B]
Get:21 http://fr.archive.ubuntu.com utopic/universe Sources [6,736 kB]
Get:22 http://fr.archive.ubuntu.com utopic/multiverse Sources [171 kB]
Get:23 http://fr.archive.ubuntu.com utopic/main i386 Packages [1,326 kB]
Get:24 http://fr.archive.ubuntu.com utopic/restricted i386 Packages [12.6 kB]
Get:25 http://fr.archive.ubuntu.com utopic/universe i386 Packages [6,183 kB]
Get:26 http://fr.archive.ubuntu.com utopic/multiverse i386 Packages [133 kB]
Get:27 http://fr.archive.ubuntu.com utopic/main Translation-en [769 kB]
Get:28 http://fr.archive.ubuntu.com utopic/multiverse Translation-en [101 kB]
Get:29 http://fr.archive.ubuntu.com utopic/restricted Translation-en [3,315 B]
Get:30 http://fr.archive.ubuntu.com utopic/universe Translation-en [4,264 kB]
Get:31 http://fr.archive.ubuntu.com utopic-updates/main Sources [7,232 B]
Get:32 http://fr.archive.ubuntu.com utopic-updates/restricted Sources [14 B]
Get:33 http://fr.archive.ubuntu.com utopic-updates/universe Sources [14 B]
Get:34 http://fr.archive.ubuntu.com utopic-updates/multiverse Sources [14 B]
Get:35 http://fr.archive.ubuntu.com utopic-updates/main i386 Packages [14.6 kB]
Get:36 http://fr.archive.ubuntu.com utopic-updates/restricted i386 Packages [14 B]
Get:37 http://fr.archive.ubuntu.com utopic-updates/universe i386 Packages [2,652 B]
Get:38 http://fr.archive.ubuntu.com utopic-updates/multiverse i386 Packages [14 B]
Get:39 http://fr.archive.ubuntu.com utopic-updates/main Translation-en [10.0 kB]
Get:40 http://fr.archive.ubuntu.com utopic-updates/multiverse Translation-en [14 B]
Get:41 http://fr.archive.ubuntu.com utopic-updates/restricted Translation-en [14 B]
Get:42 http://fr.archive.ubuntu.com utopic-updates/universe Translation-en [2,065 B]
Fetched 21.1 MB in 6s (0 B/s)
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Calculating the changes
Calculating the changes
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.
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
=== Command detached from window (Sun Nov 2 08:59:52 2014) ===
=== Command terminated with exit status 1 (Sun Nov 2 09:00:02 2014) ===
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.5
ProcVersionSignature: Ubuntu 3.13.0-39.66-generic 3.13.11.8
Uname: Linux 3.13.0-39-generic i686
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: i386
CrashDB: ubuntu
CurrentDesktop: ratpoison
Date: Sun Nov 2 09:02:04 2014
EcryptfsInUse: Yes
InstallationDate: Installed on 2010-06-10 (1605 days ago)
InstallationMedia: Ubuntu-Netbook-Remix 9.10 "Karmic Koala" - Release i386 (20091028.4)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2014-11-02 (0 days ago)
mtime.conffile..etc.update.manager.release.upgrades: 2014-11-02T08:53:30.493618
