Ubuntu 14.04 problema aggiornamenti.

Ciao a tutti.
Ho un problema con gli aggiornamenti.

In alto a destra mi appare la notifica (triangolo rosso con punto esclamativo all'interno) che dice:

The update information is outdated.

Ho provato a digitare a terminale sudo apt-get update, ma l'errore non scompare.

Inoltre digitando questo comando mi dà i seguenti errori:

Impossibile recuperare http://us.archive.ubuntu.com/ubuntu/dists/raring/main/binary-amd64/Packages  404  Not Found [IP: 91.189.91.14 80]

W: Impossibile recuperare http://us.archive.ubuntu.com/ubuntu/dists/raring/multiverse/binary-amd64/Packages  404  Not Found [IP: 91.189.91.14 80]

W: Impossibile recuperare http://us.archive.ubuntu.com/ubuntu/dists/raring/main/binary-i386/Packages  404  Not Found [IP: 91.189.91.14 80]

W: Impossibile recuperare http://us.archive.ubuntu.com/ubuntu/dists/raring/multiverse/binary-i386/Packages  404  Not Found [IP: 91.189.91.14 80]

Grazie dell'aiuto.

Edit

Posto anche l'esito del comando cat -n /etc/apt/sources.list

 1  # deb cdrom:[Ubuntu 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20140722.2)]/ trusty main restricted
 2  deb-src http://archive.ubuntu.com/ubuntu trusty main restricted #Added by software-properties
 3  
 4  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
 5  # newer versions of the distribution.
 6  deb http://it.archive.ubuntu.com/ubuntu/ trusty main restricted
 7  deb-src http://it.archive.ubuntu.com/ubuntu/ trusty main multiverse universe restricted #Added by software-properties
 8  
 9  ## Major bug fix updates produced after the final release of the
10  ## distribution.
11  deb http://it.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
12  deb-src http://it.archive.ubuntu.com/ubuntu/ trusty-updates main multiverse universe restricted #Added by software-properties
13  
14  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
15  ## team. Also, please note that software in universe WILL NOT receive any
16  ## review or updates from the Ubuntu security team.
17  deb http://it.archive.ubuntu.com/ubuntu/ trusty universe
18  deb http://it.archive.ubuntu.com/ubuntu/ trusty-updates universe
19  
20  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
21  ## team, and may not be under a free licence. Please satisfy yourself as to 
22  ## your rights to use the software. Also, please note that software in 
23  ## multiverse WILL NOT receive any review or updates from the Ubuntu
24  ## security team.
25  deb http://it.archive.ubuntu.com/ubuntu/ trusty multiverse
 26 deb http://it.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
27  
28  ## N.B. software from this repository may not have been tested as
29  ## extensively as that contained in the main release, although it includes
30  ## newer versions of some applications which may provide useful features.
31  ## Also, please note that software in backports WILL NOT receive any review
32  ## or updates from the Ubuntu security team.
33  deb http://it.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
34  deb-src http://it.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse #Added by software-properties
35  
36  deb http://security.ubuntu.com/ubuntu trusty-security main restricted
37  deb-src http://security.ubuntu.com/ubuntu trusty-security main multiverse universe restricted #Added by software-properties
38  deb http://security.ubuntu.com/ubuntu trusty-security universe
39  deb http://security.ubuntu.com/ubuntu trusty-security multiverse
40  
41  ## Uncomment the following two lines to add software from Canonical's
42  ## 'partner' repository.
43  ## This software is not part of Ubuntu, but is offered by Canonical and the
44  ## respective vendors as a service to Ubuntu users.
45  deb http://archive.canonical.com/ubuntu trusty partner
46  # deb-src http://archive.canonical.com/ubuntu trusty partner
47  
48  ## This software is not part of Ubuntu, but is offered by third-party
49  ## developers who want to ship their latest software.
50  deb http://extras.ubuntu.com/ubuntu trusty main
51  deb-src http://extras.ubuntu.com/ubuntu trusty main
52  # deb http://us.archive.ubuntu.com/ubuntu raring main multiverse