I've finally found another CD player and tested the CD in question. It
played with no distortions!
Therefore, the very frequent clicks, which I thought could be just
clipping, are after all the results of playing a copy protected CD on a
computer with digital playback :(
I ripped it with cdparanoia, bnut cdparanoia found no errors, and the
sound was the same as when playing on the computer.
Of course I can borrow the CD player, take the analog output and
re-degitize, or search for a computer with spdif in and player with
spdif out. Are there any otehr ways of tackling the protection, so I can
hear the music copy that I bought on the device of my choice?