This is happening to me as well. I am using 5.13.5460 version on an Intel Core 2 Duo 2.66 GHz, 4.0 GB RAM. It cleaned 142.8 MB in 54,073.184 seconds (15 hours) and was still not done. I have used CCleaner for years and years and never had this happen but after the last update it's crazy. I will set it to clean when I leave my desk at work every night and every morning it's not completed. I've even tried changing from Secure deletion of 35 passes to just 7 passes. If I can't use the secure deletion process then I might as well be using the browser tools to clean the history.