I have the following line in my /etc/apt/sources.list:
deb 
http://www.debian-multimedia.org etch main contrib
When I run <aptitude update> I get:
W: GPG error: 
http://www.debian-multimedia.org etch Release: The following 
signatures couldn't be verified because the public key is not available: 
NO_PUBKEY 07DC563D1F41B907
W: Couldn't stat source package list 
http://www.debian-multimedia.org 
etch/contrib Packages 
(/var/lib/apt/lists/
www.debian-multimedia.org_dists_etch_contrib_binary-i386_Packages) - 
stat (2 No such file or directory)
W: You may want to run apt-get update to correct these problems
I have spent enough time to make my husband say that I shall become rooted to 
this chair if I am not careful, unsuccessfully googling.  I have tried to 
make use of what I have found, mutatis mutandis, but am clearly mutating the 
wrong things. :-( 
I know that this has come up on the list before, but cannot find it. :-(  (Who 
said that Google was my friend???)
I would be very grateful indeed for some more pointers.
TIA
Lisi