Yup, there's something about SCSI on the AVs that isn't supported well. I have no idea what about it is different, but that's the way it is. Unfortunately for me, I learned this after I'd tracked down and installed on an 840.
The good news is that this does still see some development. There were patches posted within the last year that may provide a foundation for solving this problem. My take on it is that the smart driver ppl know what the problem is, it's just a question of getting in there and actually doing it, which would take a bit of tinkering.