Errors when doing apt-get update

[marcos89]

i get this error:
W: Duplicate sources.list entry http://security.ubuntu.com dapper-security/universe Packages (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_dapper-security_universe_binary-i386_Packages)

and i even tried replacing it with a source.list from a brand new installation but still didnt work.

here is my sources.list:
# Specialized Basic Ubuntu Multimedia Preparation Script sources.

#deb cdrom:[Ubuntu 5.10 _Breezy Badger_ - Release i386 (20051012)]/ dapper main restricted

## Uncomment the following two lines to fetch updated software from the network

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

## Uncomment the following two lines to fetch major bug fix updates produced
## after the final release of the distribution.
deb http://archive.ubuntu.com/ubuntu dapper-updates main restricted
deb-src http://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://archive.ubuntu.com/ubuntu dapper universe
deb-src http://archive.ubuntu.com/ubuntu dapper universe

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://archive.ubuntu.com/ubuntu dapper multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper multiverse

## PLF repo's.
deb ftp://ftp.free.fr/pub/Distributions_Linux/plf/ubuntu/plf/ breezy free non-free
deb-src ftp://ftp.free.fr/pub/Distributions_Linux/plf/ubuntu/plf/ breezy free non-free



and this error:

http://security.ubuntu.com/ubuntu/dists/dapper-security/universe/binary-i386/Packages.bz2: Could not open file /var/lib/apt/lists/partial/security.ubuntu.com_ubuntu_dists_dapper-security_universe_binary-i386_Packages - open (2 No such file or directory)

when it DOES exist.

what should i do?