@GrahamGo: I have no idea how Windows handles USB devices (besides stupidly), but there's no 'Kindle' driver (it's a standard USB mass storage device). Granted, that fact doesn't help you much ;p. Did you install/plug any new hardware or gadget recently? Or did anything vaguely related got updated on Windows's side?
Only one of the update blocking things is enough, and the folder trick is obviously the least intrusive/fastest/easiest one, so I'd go with that. I don't think we've ever heard of anyone complaining, so I'd go with: yep, they're both effective
.
If you really rely on nested collections and/or really can't stand the few other changes since then, then, yeah, you'll have to do the whole downgrade over diags again (you'll have to reinstall the rescue pack first).
On the other hand, If you can live with the latest version (I'm mostly referring to the collection changes), know that the basics are supported by CM
.