System update manager could not download all repository indexes

New to ubuntu and love it so far.

I have a problem with the update manager. Everytime It runs, it give me an error.

"Could not download all repository indexes

GPG error: http://ppa.launchpad.net jaunty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4874D3686E80C6B7Failed to fetch cdrom://Ubuntu 9.04 _Jaunty Jackalope_ - Release amd64 (20090420.1)/dists/jaunty/main/binary-amd64/Packages 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 9.04 _Jaunty Jackalope_ - Release amd64 (20090420.1)/dists/jaunty/restricted/binary-amd64/Packages 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.

I have no CD in the drive. The only thing I'm running on the computer is Ubuntu 9.04

Thanks for the info