I've RMA'd quite a few Maxtor drives. I don't trust them at all. The fact they give you refurbs as replacements is even worse (but then, all computer companies do that).
PowerMax is what you want, if you haven't got it already. It has always given me a proper error code with any Maxtor drive that's gone flakey on me.
BTW, did you check the cable, or use a different one? I had a cable that worked fine on one HD but not on another. I am so glad that SATA is finally here! If only more optical drives used it...
