yeah, it doe cut power off the drive if you do flip it the wrong way which might have been the problem but it doesn't seem like it.
It must be something to do with that because as soon as you dissconnect it from the motherboard it works which is exactly what mine was doing.
Have you tried using a different IDE slot? Maybe 2 instead of 1, or 1 instead of 2?
it could also be a faulty connection causing it like I said so try a different IDE cable if possible which might be doing it also, unles you used the same IDE cable on the other computer.
If you did, the only thing left is the connection on the motherboard
Hope this helps