So to spare anyone else the multiple chat sessions with Adobe support, with multiple escalations per session, here's how to fix it.
- Quit all your CS applications
- Open a terminal window.
- sudo -s
- cd '/Library/Application Support/Adobe/Adobe PCD'. You'll see a cache directory in there. Don't delete it like the tech support guy tells you to (Out of paranoia, I renamed mine instead), that'll trigger a message when you try to start a CS app telling you to reinstall CS.
- cd cache - you'll find a file named cache.db rename it to cache_broken.db.
- Open one of your CS applications. It'll ask you for the serial and this time, it'll accept it.