I went to backup my Mac mini that I am using as my apple tv server and I have a 500GB internal HD and a 500GB External HD for TM. When I run TM I get a error message that says I have 570GB taken up on my Local HD and that I need a bigger TM hard drive. How can I have 570GB on a 500GB HD? is there a cache somewhere I need to clean out? I have check and I don't have a space taken up on my local drive to backups. The purple indication under storage is 0kb. Any ideas?