Obviously you may have to manually edit your database, look for the cache settings and roll back anything you might have changed, even if the site was working.
I have been trying to find a few topics about this when they added cache options, it caused a big problem in the beginning.
Most often mistake is to enable anything other than "file" for cache, saving and then trying to navigate to your home page to see the results, not leaving a separate browser window open to change the settings back if they do not work.
This may or may not be your problem, but I have actually been through this same thing.
No, I can't figure it out.
Have you determined what it was?