HI and thanks in advance for any advice offered

I am running Debian testing

whenever I issue "apt-get update" I get the following error

W: GPG error: http: //www.debian-multimedia.org testing 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

of course running apt-get update again doesnt help the matter at all.

Here is my sources.list

#
# deb cdrom:[Debian GNU/Linux testing _Lenny_ - Official Snapshot i386 CD Binary-1 20070528-09:58]/ lenny contrib main

#deb cdrom:[Debian GNU/Linux testing _Lenny_ - Official Snapshot i386 CD Binary-1 20070528-09:58]/ lenny contrib main

#deb http://security.debian.org/ lenny/updates main contrib
#deb-src http://security.debian.org/ lenny/updates main contrib

# See sources.list(5) for more information
deb http://http.us.debian.org/debian testing main contrib non-free
#deb http://non-us.debian.org/debian-non-US testing/non-US main contrib non-free
deb http://download.skype.com/linux/repos/debian/ stable non-free
deb http://www.debian-multimedia.org testing main

Try running :
apt-get install debian-multimedia-keyring

thanks, that worked a treat,

Now I am going to push my luck !!

When I uncomment the line

#deb http://non-us.debian.org/debian-non-US testing/non-US main contrib non-free

I get the following errors

W: Couldn't stat source package list http://non-us.debian.org testing/non-US/main Packages (/var/lib/apt/lists/non-us.debian.org_debian-non-US_dists_testing_non-US_main_binary-i386_Packages) - stat (2 No such file or directory)
W: Couldn't stat source package list http://non-us.debian.org testing/non-US/contrib Packages (/var/lib/apt/lists/non-us.debian.org_debian-non-US_dists_testing_non-US_contrib_binary-i386_Packages) - stat (2 No such file or directory)
W: Couldn't stat source package list http://non-us.debian.org testing/non-US/non-free Packages (/var/lib/apt/lists/non-us.debian.org_debian-non-US_dists_testing_non-US_non-free_binary-i386_Packages) - stat (2 No such file or directory)
W: You may want to run apt-get update to correct these problems


should I just leave it commented out ?

May as well remove it I believe the non-us does not exist anymore.

non-US was deprecated when Sarge was released, go ahead and remove that part.