Could you please show us a screen capture of the exact error message you're getting?
Are you using the update mechanism in Photoshop CS6? (Help> Updates)
Also, in Photoshop, go to Help>About Plugins>Camera Raw. This will tell you which ACR version is installed.
Solved the problem by starting the installer-exe in compatibility mode for Windows 7. Strange enought, but it worked. Thanks for your efforts.
Thanks for sharing the outcome.
Glad that you were able to get things back to working.