Today many users of the cloud-based Lightroom CC application are reporting encountering the following message: “Uh-oh! Lightroom CC needs to be restarted. You’ve deleted your catalog.”
Don’t panic – just restart the application, and all should be well. Adobe is looking into this – they initially believed that “this is being triggered by a Mac OS update that is affecting Lightroom’s connection to the local database file when the system goes to sleep”, but it also seems to have been reported by people using Windows, on computers set to stay awake, and on those not performing an update.