Since I changed from reiserfs 3.6 to ext3 with debian etch amd64, the system no more suffered any crash, after days of running a very heavy computation with mpqc 2.3.1 with thread command for two dual opterons and 8 GB ram. The computation has now ended to full convergence. That was the most stressing action of memory I could conceive. Thanks to Lennart and Goswin for having guessed the most likely cause of the crashes. Cheers francesco pietra