@etilley OMG thank you so much for posting this. This exact same thing happened to me. Website was fine the night before. My site was hosted on a server that disables the ability to php email (infinityfree), so I never got the error message from this critical error. I had to edit the wp-config.php debug code to: true, in order to get the page to spit out what was wrong. Used that and googled the error message and found this post. Thank you so much for explaining how you resolved this. My client was getting worried that his site had crashed, and I thought this was going to be like finding a needle in a haystack to find what was wrong.
