Ultimamente Launchpad está dabdo problemas con la llave GPG y si eres como yo, no pude meterlos dentro de los Origines de Software en Ubuntu.

W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 60D11217247D1CFF
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY FE8956A73C5EE1C9
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 978228591BD3A65C
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY C5E6A5ED249AD24C
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 632D16BB0C713DA6
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 9BDB3D89CE49EC21
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 4874D3686E80C6B7
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 665F9AEFE1098513
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 5DC4E17435661D98
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY 28A8205077558DD0
W: GPG error: http://ppa.launchpad.net intrepid Release: The following
signatures couldn't be verified because the public key is not
available: NO_PUBKEY CA1F91146F087E5A
W: You may want to run apt-get update to correct these problems

Asi que la correción del problema pasa por la terminal. Hay que conseguir las nuevas llaves, utilizando los últimos 8 dígitos del número de error junto con el comando adecuado.

Por ejemplo, para el error

W: GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 60D11217247D1CFF

el comando sería:

$gpg --keyserver keyserver.ubuntu.com --recv 247D1CFF
$gpg --export --armor 247D1CFF | sudo apt-key add -

Dónde 247D1CFF son los últimos 8 digitos del número del error den la parte NO_PUBKEY 60D11217247D1CFF