Maybe look in BIOS for that SATAII setting. The motherboard manual has to have some info. regarding the use of SATAII in there. Then again, they tend to be very vague. Maybe you're using the SATA I drivers instead of the SATA II? I don't know if there is much of a difference in that. I was going to say that your motherboard didn't support SATAII, but you already said it does.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?