Re: What's this Silverlight thing?
@Norman: Ah, yes I had seen that, but I ran into a different issue because WSUS doesn't seem to like letting me add features in that way (see also: JP IME dictionaries and such). I'll give it another go though, as I may have solved that but forgotten that it was applicable to this issue too.
(Unless they've updated it, I still need to go through a PDF printer to make XPS into PDF though. Oy.)
(My comment was referring to how Silverlight is to Flash as XPS is to PDF, not why LO can't open them; I hadn't even considered trying that)