System Crashes after YOU update

Hi there, well, the subject says it all: my SuSE 9.0 Pro at home crashes from time to time (it powers off!!!) w/o any aparent reason and it's patched with the latest updates found by YOU yesterday night (23.05.2004). Looking at /var/log/messages I can't find any clue on what's happening; only a 'last' command shows me the damn word "crash"... Is there any other place I should take a look at to find out what's going on?? Is there any "do-it-yourself" system debug method to find the reasons for those crashes? Thanks, Martin