public key is not available

Binary package hint: update-manager

GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7889D725DA6DEEAAFailed to fetch cdrom://Ubuntu-Server 9.10 _Karmic Koala_ - Release amd64 (20091027.2)/dists/karmic/main/binary-amd64/Packages.gz Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
Failed to fetch cdrom://Ubuntu-Server 9.10 _Karmic Koala_ - Release amd64 (20091027.2)/dists/karmic/restricted/binary-amd64/Packages.gz Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
Some index files failed to download, they have been ignored, or old ones used instead.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: update-manager 1:0.134.8
ProcVersionSignature: Ubuntu 2.6.32-22.33-server 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-server x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Mon May 31 02:15:36 2010
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager