Problem solved! It was probably a Debian kernel problem, as I updated to kernel 2.6.11 and now everything works fine. Thanks, Stefano -- Stefano Calza, PhD Sezione di Statistica Medica e Biometria Dip. di Scienze Biomediche e Biotecnologie Universit? degli Studi di Brescia - Italia Viale Europa, 11 25123 Brescia email: calza@med.unibs.it Telefono/Phone: +390303717532 Fax: +390303717488 Section of Medical Statistics and Biometry Dept. Biomedical Sciences and Biotechnology University of Brescia - Italy