Pete and Mark,
The same thing happened to me. I was having problems with the first RTM build I downloaded from the beta site. For some reason, it stopped panning in virtual cockpit and spot plane mode. So I uninstalled, defragged and reinstalled. Panning was restored but I was unable to install FSUIPC4. Got the same error message as you did Mark.
Pete I totally concur with your comments about FSX being taken away from its mother too soon. It is really not ready yet. I have heard a lot of angry comments from my pilots at Mountain Air.
So now I gird my loins and hope that I can get the same results that Mark did.
Thanks so much Pete for all of your contributions.
Regards,
Verne Cotton