My iMac (3.2 GHz Intel Core i3, 16GB 1333 MHz 512MB, OS X 10.8.3 (12D78)) is set to remove trash securely. I have a rather full trash can, but when I try to empty the trash it prompts me to select whether to remove only iunlocked or all trash. I have tried both. It appears that it is starting, but stops immediately with no message as to why or that an error has happened. It simply closes the message box.