Well, whatever wayward process (be it Google's or SuccessfulHosting's) that allowed Google to write files to my domain as the 'root' user has been corrected, thanks to some timely support by the folks at SH.

Unfortunately, since Blogger doesn't have a ticket tracking system exposed, I have no way of letting them know (other than this post, I suppose) that I've resolved the problem and they can disregard my requests for help... further worsening their already dubious support levels...