Comment 5 for bug 1212483

I had this too - and I also can give some info on it:

This happend to me two times in a row (installing Luna 64bit from USB to disk) when I connected to my Wifi prior to the installation. The apt sources seemed to be totally wrecked then in the installed system ("debian sid" package sources anyone?). I think this might be a bug in the installer (as I kind of recall that I had something like this some months ago installing some ubuntu in a VM).

The third install WITHOUT connecting to Wifi before the installation (and thus not having an Internet connection during installation) then left me with a functional system (i.e. the sources seem to be sane and "apt-get update/upgrade" works).