Running Snow Leopard. Completely inexplicably, I seem to have enabled the OSX root user by accident. I honestly have no idea how it happened, but if memory serves I was looking at the login pane (with my two user accounts) when I must have hit something, and suddenly the two accounts were replaced by one that just said "Other..."

Clicking the "Other..." account allows me to type a username and password, but neither of the normal two accounts would work. Since I never set a root password, it wouldn't let me in that way either.

So I booted into Single User mode and ran these commands:

/sbin/mount -uw /
fsck -fy
launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist
dscl . -passwd /Users/root newpassword

and that let me login as root. Then, I went to System Preferences, Accounts, Login Options, clicked Join, Open Directory Utility, and lastly in the Edit menu I clicked "Disable Root User"

Great, I thought, back to normal. Except rebooting, I still only have the Other... account visible, and the root password I set beforehand doesn't work anymore! I have to reboot into Single User Mode and go through the whole process again just to get back into the system (as root)

How on Earth did I accidentally enable this? I didn't even know about the Directory Utility before now. And most importantly, why the heck would it be re-enabling the root user on boot? Thanks in advance to any help!