I was really excited to see the title of this post. Finally, I thought, someone has addressed this fairly serious problem that was introduced with 10.4.2 where several of the most popular SCSI drivers (Adaptec, Advansys etc...) were broken and there was a deafening silence from Apple regarding the issue at all. See http://discussions.apple.com/thread.jspa?threadID=141723.
Unfortunatley, the solution proposed in the parent post was simply to re-install the original driver, which for many survived intact and even worked. It's just that the drivers cause serious, catastrophic, system crashes. For me, the driver would cause a severe system crash whenever the system went to sleep. My scanner worked just fine and continues to work fine. In fact, deleting the driver was a major problem (see link above).
Use the latest installation CD/DVD to install or maintain the system software (get the CD. Pure Mac - Apple Updates (all else. Orange Micro e.g. For Orange Converter FireWire/SCSI converter FireWire SCSI FireREX1 (FireWire to Ultra SCSI Converter) by RATOC Systems, Intl. I tried two different Adaptec and one Orange Micro SCSI cards in an effort to get my old PowerLook II to work in OS X. It never worked with any iteration of OS X and either Adaptec SCSI card. It did work briefly with the Orange Micro card, with LaserSoft's SilverFast scanning software, and with Mac OS 10.1.5.
I will still download and try out the suggested driver on the hope that it will over-write the bad one that I have and perhaps not have the same problem.
Thanks for posting the link to the official driver. ---
Jaguar -- you know, the one with the Leopard spots.
Jaguar -- you know, the one with the Leopard spots.