Yeah, I think that's the entire source of the problem. I was putting together a media server, and picked up the cheapest piece of crap SATA card I could find. It wouldn't work with the first known-good SATA drive I fed it, and it *seemed* to work fine with the new SATA drive, but messing with it later, it seems... not so much.

I think I'm going to go get a better SATA card now.