Since updating to 10.5.3, all my iMac Time Machine backups contain a mystery file, alongside the Applications/System/Library folders etc. I don't like the look of it. It's called a Mach_kernal file and it takes up over 10mb. I went to the trouble of an erase/install because I suspected something unpleasant, but it still appears on every Time Machine backup. Anyone have any info on this? Is this something that needs attention? Thanks in advance.