Just a little bit ago the game froze on me, so I refreshed. I was almost through Difficult Solomon's mines (99%). I refreshed the page and it went to the home screen. All the news items were marked as "new" (I had previously looked at all of them) and all my cards were unlocked.
I have since re-locked (protected) all my cards.
Just wanted to report this. It also seems that a few people in my guild have experienced something similar.