I had this problem on a Pismo and could not for the life of me resolve it. And I tried hard. So I got another parts Pismo, swapped logic boards, and it all worked properly afterwards.

I have thought since that the trouble was either a logic board fault, or POSSIBLY an error thrown up by later ATA standards than those in play in 1998-99. The latter would, however, presumably only explain the problem if there were differences between logic board revisions. I suppose I tend to the fault explanation myself.