RAID 0 loses array

I’ve been having trouble keeping my RAID 0 array working. Seems to “lose” the array settings, I have to re-enter (I’ve been using “auto”), which means I lose my O/S. Luckily, I have a “cloned” spare simgle drive! Running a SIL 680 controller w/ 2- 40GB Maxtor 7200/ATA-133 HDD’s on a nVidia nForce2 board. I’ve tried both CS & master settings on the HDD’s. What’s Wrong?