The following signatured couldn't be verified...

["Michael S. Peek" <peek@tiem.utk.edu>]

Hi gurus,

I tried adding debian-multimedia.org to /etc/apt/sources.list and got 
the following warning:

> W: GPG error: http://debian-multimedia.org etch Release: The following 
> signatures couldn't be verified because the public key is not 
> available: NO_PUBKEY 07DC563D1F41B907
> W: You may want to run apt-get update to correct these problems
I've re-run apt-get several times as per instruction, but to no avail.  
How do I make this go away?

Thanks for your help,

Michael Peek