Indeed, we have confirmed this to be a bug, and we're working on a patch release at the moment to fix this.  We hope to have this out in a couple of days and apologise for the inconvenience in the interim. In the meantime, to make deactivating Smart Cleaning stick, the work-around is: Unchecking all of the boxes on the Options > Smart Cleaning screen in CCleaner (going from top to bottom, as the "Enable Smart Cleaning" is greyed out if "Tell me when there are junk files to clean" i