:bigsmile: Yes, maybe "reason" was a bad word. I guess I'm interested in the "cause" or "physical difference" that precludes the possibility of flashing back. Mainly because this would indicate that Plextor IS tweaking the hardware between hardware revisions, without assigning a new revision.
However, taking your point more literally, perhaps Plextor has crippled the 1.05 firware shipping with those drives to prevent people from going back to prior versions, maybe to reduce support calls? I suppose that would be a reason too, however convoluted!