I finally updated after thousands of years. As pacman was spewing, I noticed that it moved /etc/conf.d/nisdomainname to .pacsave. Uh, whatever, says I. Must be a package issue. So I just reboot...and of course ypbind can't connect to anything because nisdomainname isn't set.
Just cd to /etc/conf.d and mv nisdomainname.pacsave nisdomainname
Then it will work again.