I installed 5.7, ran ok for a while. Then it gave the error message that the preview cache was bad. A few times I have gotten this message and it restarts and repairs it. But now it couldn't. Renamed the Lightroom 5 catalog with the name "Lightroom 5_ANDERS-OFFICE8_Mar-15-230042-2015_Conflict". I got a backup and ran with that, and after a few days it happened again. It cannot repair and read the cache and shuts down.
What should I do? I can probably go to a backup again, but I keep losing work. I now backup every day.
But I need the system to be stable.
This is Windows 8.1. Lots of RAM and disk space.
The catalog isn't the problem, but rather that preview file. Use Windows Explorer or Finder (depending on your operating system) to browse to the folder that contains your catalog. Locate and delete the folder that has the extension .lrdata. Then you should be able to start Lightroom normally and it will begin generating a new cache file.
Thank you, that worked. (Thought I had tested that... dang.)