Comment 47 for bug 24234

sudo apt-get update:

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://nz.archive.ubuntu.com intrepid-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <email address hidden>
W: Failed to fetch http://nz.archive.ubuntu.com/ubuntu/dists/intrepid-updates/Release
W: Some index files failed to download, they have been ignored, or old ones used instead.

So, to fix this:

sudo apt-key advanced --keyserver subkeys.pgp.net --recv DCF9F87B6DFBCBAE

Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --keyserver subkeys.pgp.net --recv 40976EAF437D05B5
gpg: requesting key 437D05B5 from hkp server subkeys.pgp.net
gpg: key 437D05B5: "Ubuntu Archive Automatic Signing Key <email address hidden>" 2 new signatures
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg: new signatures: 2

But

sudo apt-get update

and even

sudo apt-get update -o Acquire::http::No-Cache=true

Still return errors.

This is driving me nuts. What is going on?