In an effort to get my wireless NIC working, I added a line to /etc/rc.conf and decided to reboot the system. On start-up, however, the system reported a syntax error and presented me with the option to fix it.
/usr was not mounted, so I was unable to edit the file with vi. I tried using /bin/ed to edit the file, but the system reported that the system was read-only. I was not sure what to do, but luckily the FreeBSD team has splendid documentation and FAQs.
As the FAQ states, one has to mount the root file system as read/write in order to modify any of the files. I rebooted and when presented with the syntax error, escaped to the shell. I then proceeded to mount the root file system with write access:
mount -urw /
mount -a -t ufs # for vi
After making the changes, I did a quick reboot and sure enough the problem was fixed.