It’s a day, just like any other day. You run Software Update, and it installs Safari 5.0. After re-booting, you find that Finder crashes repeatedly. You start worrying.
You then run Safari to see if anybody else on the Web has experienced the same problem. But no, Safari won’t start at all, and keeps crashing. You try to keep calm.
So you start Software Update, to see if Apple has released a patch to fix the problem… Only… “Software Update quit unexpectedly”… Aaaaaah!