Yup, I've also had a problem lately with a 52x CDrom which I tried to install (can't remember the brand off the top of my head) - A1200 wouldn't boot once IDEfix had become resident, regardless of whether CDrom was sharing an IDE channel or had one to itself.
IDEfix didn't see it as a scsi device at all, just as an ATAPI device. Don't know whether that has any relevence or not.
