1st LW 4.8.1 is not a beta version. Sounds like an issue with your computer that files should disappear. I'd do a complete system check with 'all' my utilities. Somethings not right. It may in fact be there but you can't see it. Give your Registry a clean: Here (click on link) If you don't have a registry cleaner.
Also defrag your HDD's. (One would hate to think it's due to a corrupt system.)