It happened again just now. And this time, SELinux is enabled. And here is all I can recall: I left my box for a while, when I return I found that screensaver had my box locked-up and ask for password. So I entered, and I believe I entered the right one. But my fc4 just hang up. I had to press the reboot button. Then the new kernel locked while setting up the hostname. I'm now booted with the old one, and I think another reboot with the new kernel might bring everything back to normal.
