I've installed SL on my Mac Pro from scratch (Clean Install). Then I created my first backup with Time Machine. (550GB) After two weeks, I found out that I could boot my machine into the 64 bits kernel. So I did. I booted with the 6 + 4 keys during startup and I've checked and I was using the 64bits kernel. So far so good. Then I week later without adding no new data, I caught a time machine backup with over 350GB backup. (Which match the data on my third hard drive.) I was wondering if by changing the kernel did Time Machine "thinks" that it is a new backup a take some files from my drives protected by the backup. Sorry if this seems crazy, I'm new into Macs, huge fan but very curious about how it works.