As of today, my forum threads are not sorted in order of the most recent date and time. I had it set to see the most recent posts at the beginning of the thread when I open it. Now it's all mixed up and I'm seeing posts from years ago mixed in with recent posts. Was there something changed behind the scenes recently that could have affected this?

not that I know of. there are a lot of different settings you can change that would effect only you though. mine still look fine. try going to the UCP and look around on that page.