Error I don't understand

[Pete Wright]

The error says "Check Internet Connection." Clicking details give the
results pasted below.
All my applications that use the internet are working just fine, including
Firefox.
I am running 13.04.
Why should my system be looking for 12.10 CD-ROMs?
Running Synaptic comes up with nothing needing update.
Is the system trying to look at something it thinks is installed locally?
I have been ignoring this for some time.
Any enlightenment available?
Thanks
Pete

W:Failed to fetch cdrom://Ubuntu-Studio 12.10 _Quantal Quetzal_ - Release
i386 (20121017.1)/dists/quantal/main/binary-i386/Packages  Please use
apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be
used to add new CD-ROMs
, W:Failed to fetch cdrom://Ubuntu-Studio 12.10 _Quantal Quetzal_ - Release
i386 (20121017.1)/dists/quantal/multiverse/binary-i386/Packages  Please use
apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be
used to add new CD-ROMs
, W:Failed to fetch cdrom://Ubuntu-Studio 12.10 _Quantal Quetzal_ - Release
i386 (20121017.1)/dists/quantal/restricted/binary-i386/Packages  Please use
apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be
used to add new CD-ROMs
, W:Failed to fetch cdrom://Ubuntu-Studio 12.10 _Quantal Quetzal_ - Release
i386 (20121017.1)/dists/quantal/universe/binary-i386/Packages  Please use
apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be
used to add new CD-ROMs
, E:Some index files failed to download. They have been ignored, or old
ones used instead.
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