I can't offer an explanation, but an IDE drive will hang up the interface if the IDE cable is installed upside down. Obviously you have discounted this possibility.
The IDE hdd still needs its own power cqable connects though. The sata one only powers the adapter logic.
To help others understand your setup, the following diagram may be useful:http://www.fileshosts.com/disks/sata/abit-serillel2.jpg