The only reason I think you're nuts is that I tested it in a 512k chassis with a 400k drive and original cable and it was good to go. I guess it's not entirely inconceivable that something could have gone bad in the mean time. I do know my 400k Macs (128k and 512k) are some of the pickiest I've had in regard to good floppies created with the right version of Disk Copy on System 6 with the right drive and cable blah, blah, blah. They're cranky.