Locked Myself Out - Cannot "su"

[Schiz0]

This is one of those things where after you realize what you've done,
you just want to smack yourself.

I've been working on hardening my FreeBSD 6.2-Stable box. I disabled
root login from everywhere, including the console (The box isn't
physically secure, so I didn't want anyone screwing around). Now, me
being stupid, didn't reboot after making all these changes to harden
it. So I finally rebooted (With the secure level set to 2) and I found
that I can't run "su." I get the following error:

$ su -
su: not running setuid

I can't shutdown since I can't become root, so I pulled the plug and
rebooted into single-user mode. I edited /etc/rc.conf and set
kern_securelevel_enable="NO"

I rebooted again, but for some reason I still get the same error for "su."

So basically, I locked myself out of my box completely. I fail :-(

su has the following permissions:
-r-sr-xr-x   1 root  wheel   schg   12240 May 13 13:15 su

And sudo isn't installed, unfortunately. Any ideas of how to get root back?

Thanks!