Upgrade from 13.10 to 14.04: "No new release found"

I am trying to upgrade from lubuntu 13.10 to 14.04 using

apt-get update
apt-get dist-upgrade  
do-release-upgrade

However the last command returns No new release found

I also tried do-release-upgrade -d with the same result.

/etc/apt/sources.list looks like:

# deb cdrom:[Lubuntu 13.10 _Saucy Salamander_ - Release amd64 (20131016.1)]/ saucy main multiverse restricted universe

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://de.archive.ubuntu.com/ubuntu/ saucy main restricted
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy main restricted


## Major bug fix updates produced after the final release of the
## distribution.
deb http://de.archive.ubuntu.com/ubuntu/ saucy-updates main restricted
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://de.archive.ubuntu.com/ubuntu/ saucy universe
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy universe

deb http://de.archive.ubuntu.com/ubuntu/ saucy-updates universe
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://de.archive.ubuntu.com/ubuntu/ saucy multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy multiverse

deb http://de.archive.ubuntu.com/ubuntu/ saucy-updates multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://de.archive.ubuntu.com/ubuntu/ saucy-backports main restricted universe multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ saucy-backports main restricted universe multiverse


deb http://security.ubuntu.com/ubuntu saucy-security main restricted
deb-src http://security.ubuntu.com/ubuntu saucy-security main restricted
deb http://security.ubuntu.com/ubuntu saucy-security universe
deb-src http://security.ubuntu.com/ubuntu saucy-security universe
deb http://security.ubuntu.com/ubuntu saucy-security multiverse
deb-src http://security.ubuntu.com/ubuntu saucy-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.

## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu saucy partner
# deb-src http://archive.canonical.com/ubuntu saucy partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu saucy main
deb-src http://extras.ubuntu.com/ubuntu saucy main


deb http://ppa.launchpad.net/stebbins/handbrake-releases/ubuntu raring main
deb-src http://ppa.launchpad.net/stebbins/handbrake-releases/ubuntu raring main
deb http://dl.google.com/linux/earth/deb/ stable main
# deb-src http://archive.canonical.com/ubuntu saucy partner

Note that I just upgraded lubuntu another using the same servers without problems.

File contents of /etc/update-manager/meta-releases

# default location for the meta-release file

[METARELEASE]
URI = http://changelogs.ubuntu.com/meta-release
URI_LTS = http://changelogs.ubuntu.com/meta-release-lts
URI_UNSTABLE_POSTFIX = -development
URI_PROPOSED_POSTFIX = -proposed

/etc/update-manager/release-upgrades looks like:

# some comments...

Prompt=normal

I also changed normal to lts without success.

I also checked the directory /var/lib/ubuntu-release-upgrader/ which is empty.

There is also no proxy file in /etc/apt/apt.conf.d/ so no proxy seems to be used.

The file /etc/hosts looks like:

127.0.0.1       localhost
127.0.1.1       mybox

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet

ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

So I tried every solution from Distribution upgrade problem "No new release found" without success.

Any idea what may be wrong here?

Edit

Using the graphical interface update-manager I got the error message: "Failed to download repository information"

Perhaps this gives you a hint how to solve the problem.

Edit2

I now changed from the de servers to the main servers and removed all ppas from my sources.list and sources.list.d. If possible using ppa-purge. If not I purged the relevant packages with aptitude and then removed the ppa-entries.

The ppa's where about following packages: sagemath, google-earth, handbrake, freetuxtv and julia (a math program).

However without success.

It finally worked. The problem was that I did do-release-upgrade as root, this didn't work. Invoking this command as normal user worked. Hower I don't understand why it doesn't as root.