I had a lot of hassles when I installed CS6 the main problem was that I had downloaded the free trial version and the expiry time had run out. The drama was that I had not done a proper uninstall of that trial and conflicts and errors occurred.
I searched the adobe forums and spoke to their repsand it took a while to figure it out. Some thing about registry files and the serial numbers. It was very frustrating because when it installs there are so many readers and viewers that get installed each time.