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catz, aren't you the one (or one of the main guys) working on the download module?
if you are, a buddy of mine sent me a couple of small lines of code, when implemented, they make it pretty much impossible to determine the origin/location of any download (the code hides remote *or* local file urls the same way), he uses it in several php-nuke modules that he has written, but it's regular php, not CMS-specific
if you are interested in the code, pm me and i'll find it for you (in my ICQ archives somewhere, lol)
i'm not sure if you already have something similar already in place for the Downloads module, but if not, this may help