"Unable to connect" error with apt-get?

I recently installed 12.04 but am unable to run sudo apt-get update and consequently sudo apt-get install xxx. When I run the first command I get several

Ign http://extras.ubuntu.com precise InRelease

and

Err http://extras.ubuntu.com precise release.gpg Unable to connect to extras.ubuntu.com

It works fine to wget extras.ubuntu.com.

My /etc/apt/sources.list is the original file with swedish mirrors se.archive.ubuntu.com/ubuntu. For what it is worth I have tried other mirrors with the same result. My sources.list can be found here.

Update

I am aware that there are many questions like this one, no one has helped me though. I performed the following commands with no change in result.

sudo mv /etc/apt/sources.list /etc/apt/sources.list.backup
sudo vi /etc/apt/sources.list

and pasted

################### OFFICIAL UBUNTU REPOS ###################
###### Ubuntu Main Repos
deb http://se.archive.ubuntu.com/ubuntu/ precise main 
deb-src http://se.archive.ubuntu.com/ubuntu/ precise main

###### Ubuntu Update Repos
deb http://se.archive.ubuntu.com/ubuntu/ precise-security main 
deb http://se.archive.ubuntu.com/ubuntu/ precise-updates main 
deb http://se.archive.ubuntu.com/ubuntu/ precise-proposed main 
deb http://se.archive.ubuntu.com/ubuntu/ precise-backports main 
deb-src http://se.archive.ubuntu.com/ubuntu/ precise-security main 
deb-src http://se.archive.ubuntu.com/ubuntu/ precise-updates main 
deb-src http://se.archive.ubuntu.com/ubuntu/ precise-proposed main 
deb-src http://se.archive.ubuntu.com/ubuntu/ precise-backports main

Output from wget -S --spider http://extras.ubuntu.com

Spider mode enabled. Check if remote file exists.
--2012-07-16 14:06:21--  http://extras.ubuntu.com/
Resolving ...
Connecting to ... connected.
Proxy request sent, awaiting response... 
  HTTP/1.1 200 OK
  Date: Mon, 16 Jul 2012 10:05:19 GMT
  Server: Apache/2.2.8 (Ubuntu)
  Content-Type: text/html;charset=UTF-8
  Connection: close
Length: unspecified [text/html]
Remote file exists and could contain further links,
but recursion is disabled -- not retrieving.

Output from apt-config dump

APT "";
APT::Architecture "i386";
APT::Build-Essential "";
APT::Build-Essential:: "build-essential";
APT::Install-Recommends "1";
APT::Install-Suggests "0";
APT::Authentication "";
APT::Authentication::TrustCDROM "true";
APT::NeverAutoRemove "";
APT::NeverAutoRemove:: "^firmware-linux.*";
APT::NeverAutoRemove:: "^linux-firmware$";
APT::NeverAutoRemove:: "^linux-image.*";
APT::NeverAutoRemove:: "^kfreebsd-image.*";
APT::NeverAutoRemove:: "^linux-restricted-modules.*";
APT::NeverAutoRemove:: "^linux-ubuntu-modules-.*";
APT::NeverAutoRemove:: "^gnumach$";
APT::NeverAutoRemove:: "^gnumach-image.*";
APT::Never-MarkAuto-Sections "";
APT::Never-MarkAuto-Sections:: "metapackages";
APT::Never-MarkAuto-Sections:: "restricted/metapackages";
APT::Never-MarkAuto-Sections:: "universe/metapackages";
APT::Never-MarkAuto-Sections:: "multiverse/metapackages";
APT::Never-MarkAuto-Sections:: "oldlibs";
APT::Never-MarkAuto-Sections:: "restricted/oldlibs";
APT::Never-MarkAuto-Sections:: "universe/oldlibs";
APT::Never-MarkAuto-Sections:: "multiverse/oldlibs";
APT::Periodic "";
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";
APT::Update "";
APT::Update::Post-Invoke-Success "";
APT::Update::Post-Invoke-Success:: "touch /var/lib/apt/periodic/update-success-stamp 2>/dev/null || true";
APT::Update::Post-Invoke-Success:: "[ ! -f /var/run/dbus/system_bus_socket ] || /usr/bin/dbus-send --system --dest=org.debian.apt --type=signal /org/debian/apt org.debian.apt.CacheChanged || true";
APT::Archives "";
APT::Archives::MaxAge "30";
APT::Archives::MinAge "2";
APT::Archives::MaxSize "500";
APT::Changelogs "";
APT::Changelogs::Server "http://changelogs.ubuntu.com/changelogs";
APT::Architectures "";
APT::Architectures:: "i386";
APT::Compressor "";
APT::Compressor::. "";
APT::Compressor::.::Name ".";
APT::Compressor::.::Extension "";
APT::Compressor::.::Binary "";
APT::Compressor::.::Cost "1";
APT::Compressor::.::CompressArg "";
APT::Compressor::.::CompressArg:: "";
APT::Compressor::.::UncompressArg "";
APT::Compressor::.::UncompressArg:: "";
APT::Compressor::gzip "";
APT::Compressor::gzip::Name "gzip";
APT::Compressor::gzip::Extension ".gz";
APT::Compressor::gzip::Binary "gzip";
APT::Compressor::gzip::Cost "2";
APT::Compressor::gzip::CompressArg "";
APT::Compressor::gzip::CompressArg:: "-9n";
APT::Compressor::gzip::UncompressArg "";
APT::Compressor::gzip::UncompressArg:: "-d";
APT::Compressor::bzip2 "";
APT::Compressor::bzip2::Name "bzip2";
APT::Compressor::bzip2::Extension ".bz2";
APT::Compressor::bzip2::Binary "bzip2";
APT::Compressor::bzip2::Cost "3";
APT::Compressor::bzip2::CompressArg "";
APT::Compressor::bzip2::CompressArg:: "-9";
APT::Compressor::bzip2::UncompressArg "";
APT::Compressor::bzip2::UncompressArg:: "-d";
APT::Compressor::lzma "";
APT::Compressor::lzma::Name "lzma";
APT::Compressor::lzma::Extension ".lzma";
APT::Compressor::lzma::Binary "lzma";
APT::Compressor::lzma::Cost "4";
APT::Compressor::lzma::CompressArg "";
APT::Compressor::lzma::CompressArg:: "-9";
APT::Compressor::lzma::UncompressArg "";
APT::Compressor::lzma::UncompressArg:: "-d";
APT::Compressor::xz "";
APT::Compressor::xz::Name "xz";
APT::Compressor::xz::Extension ".xz";
APT::Compressor::xz::Binary "xz";
APT::Compressor::xz::Cost "5";
APT::Compressor::xz::CompressArg "";
APT::Compressor::xz::CompressArg:: "-6";
APT::Compressor::xz::UncompressArg "";
APT::Compressor::xz::UncompressArg:: "-d";
Dir "/";
Dir::State "var/lib/apt/";
Dir::State::lists "lists/";
Dir::State::cdroms "cdroms.list";
Dir::State::mirrors "mirrors/";
Dir::State::extended_states "extended_states";
Dir::State::status "/var/lib/dpkg/status";
Dir::Cache "var/cache/apt/";
Dir::Cache::archives "archives/";
Dir::Cache::srcpkgcache "srcpkgcache.bin";
Dir::Cache::pkgcache "pkgcache.bin";
Dir::Etc "etc/apt/";
Dir::Etc::sourcelist "sources.list";
Dir::Etc::sourceparts "sources.list.d";
Dir::Etc::vendorlist "vendors.list";
Dir::Etc::vendorparts "vendors.list.d";
Dir::Etc::main "apt.conf";
Dir::Etc::netrc "auth.conf";
Dir::Etc::parts "apt.conf.d";
Dir::Etc::preferences "preferences";
Dir::Etc::preferencesparts "preferences.d";
Dir::Etc::trusted "trusted.gpg";
Dir::Etc::trustedparts "trusted.gpg.d";
Dir::Bin "";
Dir::Bin::methods "/usr/lib/apt/methods";
Dir::Bin::solvers "";
Dir::Bin::solvers:: "/usr/lib/apt/solvers";
Dir::Bin::dpkg "/usr/bin/dpkg";
Dir::Bin::lzma "/usr/bin/lzma";
Dir::Bin::xz "/usr/bin/xz";
Dir::Bin::bzip2 "/bin/bzip2";
Dir::Media "";
Dir::Media::MountPath "/media/apt";
Dir::Log "var/log/apt";
Dir::Log::Terminal "term.log";
Dir::Log::History "history.log";
Dir::Ignore-Files-Silently "";
Dir::Ignore-Files-Silently:: "~$";
Dir::Ignore-Files-Silently:: "\.disabled$";
Dir::Ignore-Files-Silently:: "\.bak$";
Dir::Ignore-Files-Silently:: "\.dpkg-[a-z]+$";
Dir::Ignore-Files-Silently:: "\.save$";
Dir::Ignore-Files-Silently:: "\.orig$";
Dir::Ignore-Files-Silently:: "\.distUpgrade$";
Acquire "";
Acquire::cdrom "";
Acquire::cdrom::mount "/media/cdrom/";
Acquire::Languages "";
Acquire::Languages:: "en_US";
Acquire::Languages:: "en";
Acquire::Languages:: "none";
Aptitude "";
Aptitude::Get-Root-Command "sudo:/usr/bin/sudo";
Unattended-Upgrade "";
Unattended-Upgrade::Allowed-Origins "";
Unattended-Upgrade::Allowed-Origins:: "${distro_id}:${distro_codename}-security";
DPkg "";
DPkg::Pre-Install-Pkgs "";
DPkg::Pre-Install-Pkgs:: "/usr/sbin/dpkg-preconfigure --apt || true";
DPkg::Post-Invoke "";
DPkg::Post-Invoke:: "if [ -d /var/lib/update-notifier ]; then touch /var/lib/update-notifier/dpkg-run-stamp; fi; if [ -e /var/lib/update-notifier/updates-available ]; then echo > /var/lib/update-notifier/updates-available; fi ";
CommandLine "";
CommandLine::AsString "apt-config dump";

apt-get is not obeying your system-wide proxy settings.

• Create a file called 95proxies in /etc/apt/apt.conf.d/, and include the following:

  Acquire::http::proxy "http://www-proxy.ericsson.se:8080/";
  Acquire::ftp::proxy "ftp://www-proxy.ericsson.se:8080/";
  Acquire::https::proxy "https://www-proxy.ericsson.se:8080/";
  

Finally, logout and reboot to make sure the changes take effect.

That should hopefully fix your apt-get "unable to connect" problem.

Go to Ubuntu Software in Software & Updates and try changing the Download from: to Main Server