DQE(DriveQueueEntry) might be active (should be inactive).
This must be drivers fault.

I'd like to add 1 instruction to John san's.
0) Don't use aux driver (INIT/CDEV...) for the target drive.

> 1) Unplug the power cable going to the hard drive
> 2) Boot off of the CD
> 3) After booting is complete, plug the power cable into the hard drive
> 4) Run Apple HD SC
> 
> This works most of the time. Otherwise, you can bring the drive to another
> computer with SCSI and perform a low level format (should be easy on an
> Amiga or a PC running NetBSD).
> 
> John Klos

Takuji Matsugaki