I don't know about anyone else, but after installing the new Beta of Safari 4 my Finder kept dying. Poor beast would lock up. I'd force quit her and she'd never come back to life. The only way I could get her back was to either A) hard reboot with the metal button on the front of my tower (a PPC G5, mind you), or B) SSH in and: sudo killall loginwindow
Bummer.
Since uninstalling it, using the included uninstaller (which also hung after the "Restart" prompt, forcing a hard reboot), the problem has cleared up.
Anyway, this is just my experience, but word to the wise people. Beta means beta.
Oh well. Moving on.
