If your system config was able to run O'Hare before the update, it should work.
The suggestions are always the same:
- Turn off your antivirus, or exclude the FS9\modules folder from scanning
- Reboot Windows, do not launch FS9, clear your browser cache, and launch the setup.
- Under Vista, try turning off DEP and/or UAC, search on this forum, there are several threads about how to do it
- If you have changed your FS9.EXE (changing between the official version and a nocd version, or patching for >2GB) you need to run the setup again, so it will download the correct version for your executable.