Update Issue

Hello.

This is most likely something simple but when I ran: apt-get update I get the following errors:

W: There is no public key available for the following key IDs:
4D270D06F42584E6
W: GPG error: http://archive.debian.org lenny/updates Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9AA38DCD55BE302B
W: You may want to run apt-get update to correct these problems

I have tried:

apt-get clean
apt-get install debian-keyring
apt-get update

But nothing seems to want to fix this error? What should I be running?

Paul