can't update

Hm. Are you sure to be connected to the internet? Maybe you have to set a proxy? Does it work on the other PCs?

of course i am connected this is the pc i am providing these informations.
I don't know how to set up a proxy
The other Pc's have also the same problem

It worked some time ago, right? Can you show us the file /etc/apt/sources.list? Thank you!

these are the contents of my /etc/apt/sources.list
# Automatically generated sources.list
# http://www.ubuntu-nl.org/source-o-matic/
#
# If you get GPG errors with this sources.list, locate the GPG key in this file
# and run these commands (where KEY is replaced with that key)
#
# gpg --keyserver hkp://subkeys.pgp.net --recv-keys KEY
# gpg --export --armor KEY | sudo apt-key add -
#
# If you don't know what to do with this file, read
# https://help.ubuntu.com/community/Repositories/CommandLine

# Ubuntu supported packages
# GPG key: 437D05B5
deb http://archive.ubuntu.com/ubuntu/ gutsy main restricted
deb http://archive.ubuntu.com/ubuntu/ gutsy-updates main restricted
deb http://archive.ubuntu.com/ubuntu/ gutsy-security main restricted

deb-src http://archive.ubuntu.com/ubuntu/ gutsy main restricted
deb-src http://archive.ubuntu.com/ubuntu/ gutsy-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu/ gutsy-security main restricted

# Ubuntu community supported packages
# GPG key: 437D05B5
deb http://archive.ubuntu.com/ubuntu/ gutsy universe multiverse
deb http://archive.ubuntu.com/ubuntu/ gutsy-updates universe multiverse
deb http://archive.ubuntu.com/ubuntu/ gutsy-security universe multiverse

deb-src http://archive.ubuntu.com/ubuntu/ gutsy universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ gutsy-updates universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ gutsy-security universe multiverse

Okay. Should work. And what errors do you get?

it seems that it tries to conect to the server for example (80.125.111.100) i don't remember exactly the number the time is passing and there's no progress of fownloading any updates. then it goes to next server and the same.
I have to remind you that i use an adsl router modem which i connect to the PC's

Hm. This should not be a problem, because internet seems to work, right? Can you try to ping the servers? Open a terminal (Applications > Accessoires >> Terminal/Console) and type "ping [ip adress]". Do you get an answer?

if i write ping [ip adress] it tells me: unknown host [ip
if i type ping www.yahoo.com i get:
PING www.yahoo-ht3.akadns.net (87.248.113.14) 56(84) bytes of data.
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=1 ttl=51 time=95.2 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=2 ttl=51 time=96.3 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=3 ttl=51 time=96.4 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=4 ttl=51 time=94.7 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=5 ttl=51 time=95.8 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=6 ttl=51 time=96.0 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=7 ttl=51 time=95.8 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=8 ttl=51 time=96.6 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=9 ttl=51 time=95.4 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=10 ttl=51 time=95.6 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=11 ttl=51 time=95.7 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=12 ttl=51 time=96.5 ms
64 bytes from www.yahoo.com (87.248.113.14): icmp_seq=13 ttl=51 time=95.1 ms

Okay. Type:
ping 80.125.111.100
and
ping archive.ubuntu.com
and post the results here!

the results from the second ping are:
pc02@pc02-desktop:~$ ping archive.ubuntu.com
PING archive.ubuntu.com (91.189.88.46) 56(84) bytes of data.
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=1 ttl=50 time=90.9 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=2 ttl=50 time=91.7 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=3 ttl=50 time=91.5 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=4 ttl=50 time=90.0 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=5 ttl=50 time=90.1 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=6 ttl=50 time=92.1 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=7 ttl=50 time=91.6 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=8 ttl=50 time=88.4 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=9 ttl=50 time=92.0 ms
64 bytes from archive.ubuntu.com (91.189.88.46): icmp_seq=10 ttl=50 time=92.0 ms

from the first:
pc02@pc02-desktop:~$ ping 80.125.111.100
PING 80.125.111.100 (80.125.111.100) 56(84) bytes of data.

and it stays there, i mean it doesn't go further

Can you connect http://archive.ubuntu.com/ubuntu/ with a webbrowser like Firefox? Do you have to use a proxy to connect to the internet?

of course i can.
this is what i see
Index of /ubuntu

Icon Name Last modified Size [DIR] Parent Directory -
[DIR] dists/ 18-Oct-2007 17:18 -
[DIR] indices/ 08-Dec-2007 09:47 -
[ ] ls-lR.gz 08-Dec-2007 09:46 5.6M
[DIR] pool/ 21-Jun-2007 05:03 -
[DIR] project/ 15-Jun-2004 15:21

Sorry i don't use a proxy server

Hm. This is very strange. Maybe this is a bug. So please file a bugreport here: https://bugs.launchpad.net/ubuntu/+filebug