I have Net connection OK but when I do an "apt-get update" I get error messages (Could not create a socket for 2001:7a8:1:5::14 (f=10 t=1 p=6) - socket (97 Address family not supported by protocol) [IP: 2001:7a8:1:5::14 21])
and it fails to connect and times out. I tried this on Ubuntu and mepis;the result is the same on each.
All the trouble started when they installed a different router at work(Netcomm ADSL2+ Modem Router) and the only way to get an Internet connection was to choose DHCP instead of static IP address(Windows as well).
I've checked the DNS server address, appears to be OK. Have spent hours and hours on this. Any clues?

Contents of /etc/apt/sources.list

# See sources.list(5) for more information, especialy

# This file may be edited by the MEPIS System Center
# Do not modify the comments manually!
# Change sources only in the section at the end of this file!

# Primary
deb ftp://ftp.us.debian.org/debian testing main contrib non-free
#deb-src ftp://ftp.us.debian.org/debian testing main contrib non-free
deb ftp://ftp.us.debian.org/debian unstable main contrib non-free
#deb-src ftp://ftp.us.debian.org/debian unstable main contrib non-free

# non-us
deb ftp://non-us.debian.org/debian-non-US testing/non-US main contrib non-free
#deb-src ftp://non-us.debian.org/debian-non-US testing/non-US main contrib non-free
deb ftp://non-us.debian.org/debian-non-US unstable/non-US main contrib non-free
#deb-src ftp://non-us.debian.org/debian-non-US unstable/non-US main contrib non-free

# MEPIS cds
#deb file:/mnt/cdrom unstable main

# MEPIS apt pool - specific packages available on-line
deb http://apt.mepis.org/3.3 unstable main

# DO NOT EDIT ABOVE THIS LINE
# mplayer
deb ftp://ftp.nerim.net/debian-marillat/ unstable main
----------------------------------------------------------------

You should post your /etc/apt/sources.list

Backup your sources.list and change everything ftp://ftp.us.debian.org/ to http://mirrors.kernel.org/debian and see what that does.