I was having a problem with my system logging out and wanting to shut down if I left it alone for more than 2 hours. I could not figure out what was wrong with the software and pre-purchased leopard thinking this was an easy fix. Just install a new OS instead of reinstalling tiger and doing hours of updates. Well, I was looking in the security prefs in the system prefs and the "logout if inactive" was turned on!!! wooo hooo, I must have turned on when I was drinking! I'm such an idiot!!!!!