For some reason now, if I go to Manage Search Engines within Firefox (click on the search bar dropdown, and click Manage Search Engines..), click Edit Keyword, type in a keyword, and click OK, I can no longer click the
second OK, as seen in the screenshot. This happens even in safe mode. It did happen right after trying to work with some Search mode plugins (Web Search Pro), however that is now uninstalled, and it happens even in safe modes with addons disabled.
Going to try in order unless someone has a better idea:
1. Reinstalling this version of Firefox
2. Reverting to previous version of Firefox