Alrighty, the most random thing has fixed my drives.
I replaced the IDE cable.
Never woulda thunk.....*wanders off ranting to self about IDE cables and flux capacitors*
Hmm... could you have pulled them just a little loose when you were replacing the PSU? Either way, glad you got it sorted.
IDE technology is much like hard drive technology.
It's a serious miracle that either of them work at all.
A multimeter attached to the right channels would've sorted this out a loooong time ago. Although you might need to go out of your way to expose them...