Possible Duplicate:
How do I fix the GPG error “NO_PUBKEY” without terminal?
I get this message when I use Update-Manager:
W: GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9BDB3D89CE49EC21
I have no idea what's wrong and how to fix it. Could someone kindly explain what I need to do to fix whatever is wrong? Is there a way to prevent this from happening in the future?
