Synaptic cannot access repositories

I am unable to install any packages with either the basic add/remove tool or via synaptic, because neither one can communicate properly with the servers.  I think this may be because I am on a network that uses DHCP, but I don't know how to correct the problem.  I can do simple things like access the internet through firefox, so it's not a hardware problem.  Here is the full text of the error message I get:Could not download all repository indexesThe repository might be no longer available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and the correct writing of the repository address in the preferences.http://archive.ubuntu.com/ubuntu/dists/dapper/Release.gpg: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-updates/Release.gpg: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://security.ubuntu.com/ubuntu/dists/dapper-security/Release.gpg: The HTTP server sent an invalid reply headerhttp://archive.ubuntu.com/ubuntu/dists/dapper-backports/Release.gpg: Connection failed [IP: 195.248.90.38 80]http://archive.canonical.com/ubuntu/dists/dapper-commercial/Release.gpg: The HTTP server sent an invalid reply headerhttp://packages.freecontrib.org/plf/dists/dapper/Release.gpg: The HTTP server sent an invalid reply headerhttp://packages.freecontrib.org/plf/dists/dapper/free/binary-i386/Packages.gz: The HTTP server sent an invalid reply headerhttp://packages.freecontrib.org/plf/dists/dapper/non-free/binary-i386/Packages.gz: Connection failedhttp://packages.freecontrib.org/plf/dists/dapper/free/source/Sources.gz: The HTTP server sent an invalid reply headerhttp://packages.freecontrib.org/plf/dists/dapper/non-free/source/Sources.gz: The HTTP server sent an invalid reply headerhttp://archive.canonical.com/ubuntu/dists/dapper-commercial/main/binary-i386/Packages.gz: The HTTP server sent an invalid reply headerhttp://archive.ubuntu.com/ubuntu/dists/dapper/main/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.35 80]http://archive.ubuntu.com/ubuntu/dists/dapper/restricted/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.35 80]http://archive.ubuntu.com/ubuntu/dists/dapper/universe/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper/multiverse/binary-i386/Packages.gz: Connection failed [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper/universe/binary-i386/Packages.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper/main/binary-i386/Packages.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper/restricted/binary-i386/Packages.gz: Connection failed [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper/multiverse/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-updates/main/binary-i386/Packages.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-updates/restricted/binary-i386/Packages.gz: Connection failed [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-updates/main/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-updates/restricted/source/Sources.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-backports/main/binary-i386/Packages.gz: Connection failed [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-backports/restricted/binary-i386/Packages.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-backports/universe/binary-i386/Packages.gz: The HTTP server sent an invalid reply header [IP: 195.248.90.38 80]http://archive.ubuntu.com/ubuntu/dists/dapper-backports/multiverse/binary-i386/Packages.gz: Connection failed [IP: 195.248.90.38 80]http://security.ubuntu.com/ubuntu/dists/dapper-security/main/binary-i386/Packages.gz: The HTTP server sent an invalid reply headerhttp://security.ubuntu.com/ubuntu/dists/dapper-security/restricted/binary-i386/Packages.gz: The HTTP server sent an invalid reply headerhttp://security.ubuntu.com/ubuntu/dists/dapper-security/main/source/Sources.gz: The HTTP server sent an invalid reply headerhttp://security.ubuntu.com/ubuntu/dists/dapper-security/restricted/source/Sources.gz: The HTTP server sent an invalid reply headerhttp://security.ubuntu.com/ubuntu/dists/dapper-security/universe/binary-i386/Packages.gz: Connection failedhttp://security.ubuntu.com/ubuntu/dists/dapper-security/universe/source/Sources.gz: The HTTP server sent an invalid reply header

synaptic

I don't think dhcp has something to do with it. When you can browse with firefox then you have a correct connection. This is for me also new, but when I look here : http://everythingelse.wordpress.com/2006/10/23/howto-install-flash-9-bet... your problem looks to be something with gpg. hth.

Repositories

Have a look at https://help.ubuntu.com/community/Repositories/UbuntuBe yourself and never prevent others from being themselves