And your scsi setup is like this?
Terminator===CSPPC===IDE HDD (termpwr ON(on the adapter)===CD Drive (TermPwr ON (on the adapter)=== Terminator
Have you tried running the whole scsi chain in 8bit instead of 16bit? If you do so, disable all the ID you do not use in the PPC bios and sett the HDD and SCSI to 8bit.
Do not know if an IDE hdd works like an 50pin scsi, if it do you will need to terminate the 8bits that is left over if you run in 16bit mode and to do so you need term pwr on the IDE or CD.