The whole site was broken. The front end was fine and working. While updating some extensions it would go through part of the update and then I would just get this screen.
I refreshed the page and had to “resend” the information and the update finished. It was the JCE Pro component that got hung, but I had others such as Akeeba Admin Tools that also go hung.
I have tried just refreshing the page before it didn’t fix the issue. I was glad it worked this time. I am not sure what the issue is. I seems to have just started happening this week.
I hope this helps someone else out there…