I received the same exact error! Same thing — worked last night, and doesn’t work today. I can’t even log into the back end… all avenues lead to the error.
Just wanted to update on this — checked in the back end, and the comments are there. They also exist on the post pages. The only place they don’t show are in the comment counts on the main page — every post shows as “No Comments”. Is there any way I can update these to reflect the real numbers?