The problem I mentioned was solved. Nothing to do with sane, the issue was the version of hplip. Ubuntu offered version 3.9.2, which was apparently buggy or had a problem with this particular printer. I installed version 3.9.4b and it's all right.
Posted this solution should someone else face the same problem. Thanks, Guido (Italy) -- Guido Milanese - Professor of Latin The Catholic University, Milan and Brescia, Italy http://docenti.unicatt.it/milanese_guido http://www.arsantiqua.org
