Repo problem

[O. Sinclair]

Am I the only one getting this message after 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://archive.ubuntu.com hardy-security 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


Given that I have just run "sudo aptitude update" and/or "sudo apt-get 
update" I dont think the suggested solution helps ;-)

Regards,
Sinclair