Hi, when I got my Mac for the first time and plugged my USB in, there was some stuff I didn't need anymore, so I deleted it. Now, whenever I try to securely empty my trash, it won't let me remove anything from my USB because I don't "have permission to access some of the following items. I went into Disk Utility, backed up all of my stuff, formatted it and the same problem occurs once I have put my files back in and delete something else. I can access all of these files perfectly when they aren't in the trash. Can anyone help?