$ sudo apt-get update
Get:1 http://se.archive.ubuntu.com dapper Release.gpg [189B]
Get:2 http://se.archive.ubuntu.com dapper-updates Release.gpg [189B]
Get:3 http://security.ubuntu.com dapper-security Release.gpg [189B]
Get:4 http://kubuntu.org dapper Release.gpg [191B]
Get:5 http://se.archive.ubuntu.com dapper-backports Release.gpg [189B]
Hit http://se.archive.ubuntu.com dapper Release
Hit http://se.archive.ubuntu.com dapper-updates Release
Hit http://security.ubuntu.com dapper-security Release
Hit http://kubuntu.org dapper Release
Hit http://se.archive.ubuntu.com dapper-backports Release
Hit http://se.archive.ubuntu.com dapper/main Packages
Hit http://se.archive.ubuntu.com dapper/restricted Packages
Hit http://se.archive.ubuntu.com dapper/main Sources
Hit http://security.ubuntu.com dapper-security/main Packages
Hit http://se.archive.ubuntu.com dapper/restricted Sources
Hit http://se.archive.ubuntu.com dapper/universe Packages
Hit http://se.archive.ubuntu.com dapper/universe Sources
Hit http://se.archive.ubuntu.com dapper/multiverse Packages
Hit http://se.archive.ubuntu.com dapper/universe Packages
Hit http://kubuntu.org dapper/main Packages
Hit http://se.archive.ubuntu.com dapper-updates/main Packages
Hit http://se.archive.ubuntu.com dapper-updates/restricted Packages
Hit http://se.archive.ubuntu.com dapper-updates/main Sources
Hit http://se.archive.ubuntu.com dapper-updates/restricted Sources
Hit http://security.ubuntu.com dapper-security/restricted Packages
Hit http://security.ubuntu.com dapper-security/main Sources
Hit http://security.ubuntu.com dapper-security/restricted Sources
Hit http://se.archive.ubuntu.com dapper-updates/multiverse Packages
Hit http://se.archive.ubuntu.com dapper-updates/universe Packages
Get:6 http://se.archive.ubuntu.com dapper-backports/main Packages [5292B]
Hit http://se.archive.ubuntu.com dapper-backports/restricted Packages
Hit http://se.archive.ubuntu.com dapper-backports/universe Packages
Hit http://se.archive.ubuntu.com dapper-backports/multiverse Packages
Get:7 http://se.archive.ubuntu.com dapper-backports/main Sources [3486B]
Hit http://se.archive.ubuntu.com dapper-backports/restricted Sources
Hit http://se.archive.ubuntu.com dapper-backports/universe Sources
Hit http://se.archive.ubuntu.com dapper-backports/multiverse Sources
Hit http://security.ubuntu.com dapper-security/universe Packages
Hit http://security.ubuntu.com dapper-security/universe Sources
Hit http://security.ubuntu.com dapper-security/multiverse Packages
Hit http://security.ubuntu.com dapper-security/universe Packages
Fetched 8783B in 0s (13.0kB/s)
Failed to fetch http://se.archive.ubuntu.com/ubuntu/dists/dapper-backports/main/binary-i386/Packages.bz2  MD5Sum mismatch
Failed to fetch http://se.archive.ubuntu.com/ubuntu/dists/dapper-backports/main/source/Sources.bz2  MD5Sum mismatch
Reading package lists... Done
E: Some index files failed to download, they have been ignored, or old ones used instead.

__________________________________________________________________________

sources.list looks like this:

# 
# deb cdrom:[Ubuntu 6.06.1 _Dapper Drake_ - Release i386 (20060807.1)]/ dapper main restricted


# deb cdrom:[Ubuntu 6.06.1 _Dapper Drake_ - Release i386 (20060807.1)]/ dapper main restricted

deb http://se.archive.ubuntu.com/ubuntu/ dapper main restricted
deb-src http://se.archive.ubuntu.com/ubuntu/ dapper main restricted

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

## Uncomment the following two lines to add software from the 'universe'
## repository.
## 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
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://se.archive.ubuntu.com/ubuntu/ dapper universe
deb-src http://se.archive.ubuntu.com/ubuntu/ dapper universe

## Uncomment the following two lines to add software from the 'backports'
## repository.
## 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://se.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse
deb-src http://se.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse


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

deb http://kubuntu.org/packages/amarok-143 dapper main