Ubuntuupdate reports a key error.

An Ubuntu12.04beta1 version is installed. When I apt-getupdate reports an error W: GPGerror: http://security.ubuntu.comprecise-securityRelease: Thefollowingsignatureswereinvalid: BADSIG40976EAF437D05B5UbuntuArchive

A Ubuntu 12.04 beta1 version is installed.

When I

Apt-get update

An error is reported.

W: GPG error: http://security.ubuntu.com precise-security Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key

I cannot change the source. It is the same if I change it to a foreign country.

Sudo apt-get clean
Cd/var/lib/apt
Sudo mv lists. old
Sudo mkdir-p lists/partial
Sudo apt-get clean
Sudo apt-get update

This is done.

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