Didn't work for me:(

Running Lucid x64

When I reload repositories from the UK or Main server in Synaptic I get the following error message:-

GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4EA3A911D48B8E25GPG error: http://deb.opera.com stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F9A2F76A9D1A0061GPG error: http://download.virtualbox.org lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 54422A4B98AB5139Failed to fetch http://apt.spideroak.com/ubuntu-spideroak-lucid/dists/release/restricted//binary-amd64/Packages.gz  404  Not Found
Some index files failed to download, they have been ignored, or old ones used instead.

My sources list is:-

# deb cdrom:[Ubuntu 10.04 LTS _Lucid Lynx_ - Release amd64 (20100429)]/ lucid main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

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

## Major bug fix updates produced after the final release of the
## distribution.
deb http://gb.archive.ubuntu.com/ubuntu/ lucid-updates main restricted
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://gb.archive.ubuntu.com/ubuntu/ lucid universe
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid universe
deb http://gb.archive.ubuntu.com/ubuntu/ lucid-updates universe
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-updates universe

## 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 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://gb.archive.ubuntu.com/ubuntu/ lucid multiverse
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid multiverse
deb http://gb.archive.ubuntu.com/ubuntu/ lucid-updates multiverse
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://gb.archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse
# deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu lucid partner
# deb-src http://archive.canonical.com/ubuntu lucid partner

deb http://gb.archive.ubuntu.com/ubuntu/ lucid-security main restricted
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-security main restricted
deb http://gb.archive.ubuntu.com/ubuntu/ lucid-security universe
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-security universe
deb http://gb.archive.ubuntu.com/ubuntu/ lucid-security multiverse
deb-src http://gb.archive.ubuntu.com/ubuntu/ lucid-security multiverse
deb http://download.virtualbox.org/virtualbox/debian lucid non-free
deb http://apt.spideroak.com/ubuntu-spideroak-lucid release restricted/
deb http://archive.canonical.com/ lucid partner
deb http://deb.opera.com/opera/ stable non-free

This has only started happening in the last few days so I'm wondering if it's due to an update.

My DNS is set to:-

# Generated by NetworkManager
nameserver 208.67.222.222
nameserver 208.68.220.220

This values are both set in my router AND manually in my Network Manager set up.

I also have a similar problem with my laptop which is running Karmic on the same network. The DNS is the same though the sources are slightly different.