I had a power outage in the middle of an import of photos. now lightroom only gives an error message--lightroom encountered an error when reading from its preview cache and needs to close. Any ideas how to fix?
Browse to the folder that contains your catalog and locate a folder with the extension .lrdata and delete that folder. You may also see a file with the .lock extension. If you do, that file needs to be deleted as well. Then, start Lightroom.