At some point, I ended up resetting the config file by doing the following:
setenv cfgfile default1.cfg
saveenv
reset
After the upgrade, the controller would reboot but present an "undefined Controller Setup" message when connecting via web browser. It was thought that the above commands would fix that, but evidently not without other unintended effects.
The original configuration I had on the controller is not important to me; I'm only looking to set the controller up as standalone with 1 or 2 access points. With that said, is there a particular file I should revert to instead?