To be clear, I didn't just randomly decide to run Uru with admin permissions, I was having legit problems with things like the Virtual Store that you just mentioned and Uru just plain old acting strange and crashing. Setting it to admin privileges is what FIXED those issues from happening for me. But confusingly it sounds like it caused the problems for other people? There's just no winning running old games I guess.
(Trying to remember the old times)
So I think if you actually made every program that ever has to work with Uru's files have admin permissions (including Drizzle, e.g. when adding MOUL files to your Uru:CC installation), that would probably work.
But the more reliable solution, we found, is to put Uru into a place where admin permissions are needed for nobody (instead of for everybody) -- which is to move Uru into your local user profile and start it there. And at that place it is crucial not to use admin permissions for anything as it doesn't work when you mix and match.
(I should also mention that at this point, I'd have a really hard time changing that error message. I do have the source code for this starter somewhere, but I totally lost the build environment, so trying to re-build that binary could be "fun". It's not a big or complicated one, but it does depend on Qt 4, which is long dead and deprecated by now.)