Which ID have you set for the existing HD and the new one?
I suggest ID0 for the OLD HD and ID1 for the NEW one.
Goto the CSPPC Early BootMenu in the SCSI section (hit ESC during the boot) and check the values for the 2 HDs. (both set to LUN 1)
Leave all to AUTO (bus-mount) Synchron ON
Try also to set the Reset delay (in the ID7-Controller) to 2 seconds.
Good luck :-)
EDIT- ah and try from a shell
version cybppc.device FULL
and post here the version
assuming you have the SCSI chain set as:
ActTerminator >>>> CSPPC >>>> HD-ID0 >>>> HD-ID1 >>>>> ActTerminator
