Failed to update packages: GPG Error with BADSIG as returned message

[Tobias Dausend]

Today I've tried to update my Ubuntu 12.04 and got the following message in return:

W: GPG error: http://de.archive.ubuntu.com precise-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <email address hidden>

I've tried also my both installations with elementaryOS and got this error message again.

[Tobias Dausend (b-infj-j)]

Additional information: There was no change within packages for the last days and the last updates on the weekend were without problems done.

[Anton Frick (anton-frick)]

Had the same problem yesterday.

W: GPG error: http://de.archive.ubuntu.com trusty-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <email address hidden>

An hour later the trusty-updates Release.gpg was updated according to the ftp's file timestamp and everything seemed to work properly again.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Alexey Degtyarev (adegtyarev)]

The same here on Trusty:

# apt-get update
...
...
Fetched 297 kB in 2s (111 kB/s)
W: GPG error: http://de.archive.ubuntu.com trusty-backports Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <email address hidden>
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/de.archive.ubuntu.com_ubuntu_dists_trusty-updates_main_binary-amd64_Packages Hash Sum mismatch

E: Some index files failed to download. They have been ignored, or old ones used instead.
# echo $?
100

[nh2 (nh2)]

Is this an error only with the .de mirror? It is still there.