Possibly due to a heat problem. This has been reported under the following conditions:1) The core system is installed in a 9600 and the back cover is not in place, so the airflow kit which is fixed on this cover doesn't work. Even if the 9600 is " opened," the cards need airflow.2) Not enough airflow for the hard drive(s), particularly the high RPM drives like the Cheetahs. 3) ATTO card is a " new " model. These SCSI accelerator cards seem to be more sensitive to the heat produced in the following cases: - When 4 or more cards are installed in the Mac - When a lot of RAM is installed in the Mac. - When 32 dense tracks are recorded or played simultaneously.