9.04 won't upgrade

[Defenestrator09]

Whenever I try to check for updates in Ubuntu 9.04 I get this message:

"W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://security.ubuntu.com jaunty-security Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: GPG error: http://us.archive.ubuntu.com jaunty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://us.archive.ubuntu.com jaunty-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/jaunty-security/Release

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/jaunty-updates/Release

W: Some index files failed to download, they have been ignored, or old ones used instead."

I am completely clueless about what to do. Has anyone run into something like this before or know how to fix it to allow me to download upgrades?

[tommcd]

Try importing the GPG key for the repositories. See this:
http://ubuntuforums.org/showthread.php?t=1238623
Be sure to replace the EF4186FE247510BE code in that example with the code in your error message.
Perhaps the GPG key server is just down, or a little slow. Try it again later.

If this does not work then try a different mirror.

And welcome to the Ubuntu forums!