I did something *really* stupid last night. I had wiped my laptop clean and installed FreeBSD 4.6 (my connection isn't good enough to download 4.6.2). After I had gotten X working I tried to get a DVD player working. To fix a bug with one of the libraries I updated ports and tried to delete the old libdvdcss.
Instead of running "pkg_delete -f libdvdcss-1.1.2", I ran "pkg_delete -a libdvdcss-1.1.2". For those who aren't familiar with FreeBSD, "pkg_delete -a" deletes all packages you've installed on your system (excluding the base system). You can imagine the amount of anguish I had to go through for the next four hours getting everything running again. I can play DVD discs in FreeBSD now though.