Problem with apt-update

[Guilherme H. Polo G.]

I just tried doing an apt-update and I got the following problem:

root at art:~ # apt-get update
Get:1 http://br.archive.ubuntu.com breezy Release.gpg [189B]
Get:2 http://br.archive.ubuntu.com breezy-updates Release.gpg [189B]
Get:3 http://security.ubuntu.com breezy-security Release.gpg [189B]
Hit http://br.archive.ubuntu.com breezy Release
Hit http://security.ubuntu.com breezy-security Release
Ign http://br.archive.ubuntu.com breezy Release
Hit http://br.archive.ubuntu.com breezy-updates Release
Hit http://security.ubuntu.com breezy-security/main Packages
Hit http://br.archive.ubuntu.com breezy/main Packages
Hit http://br.archive.ubuntu.com breezy/restricted Packages
Hit http://security.ubuntu.com breezy-security/restricted Packages
Hit http://security.ubuntu.com breezy-security/universe Packages
Hit http://br.archive.ubuntu.com breezy/main Sources
Hit http://br.archive.ubuntu.com breezy/restricted Sources
Hit http://br.archive.ubuntu.com breezy/universe Packages
Hit http://br.archive.ubuntu.com breezy-updates/main Packages
Hit http://br.archive.ubuntu.com breezy-updates/restricted Packages
Hit http://br.archive.ubuntu.com breezy-updates/main Sources
Hit http://br.archive.ubuntu.com breezy-updates/restricted Sources
Fetched 191B in 2s (81B/s)
Reading package lists... Done
W: GPG error: http://br.archive.ubuntu.com breezy Release: The following
signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive
Automatic Signing Key < ftpmaster at ubuntu.com>
W: You may want to run apt-get update to correct these problems
root at art:~ #
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I did apt-update again and still got this problem. I would like to know
if someone else is getting this problem too and a possible fix to it.
Thanks