Have you tried just turning it off then on again. Full shutdown so it asks you "Do you want to shut down?"
That usually works for me when the double arrow circle keeps going and going.
I've never had that error message though so I don't know if that would work. It is worth a try though, much less drastic than unregistering or reformatting.
Maybe someone else knows a better answer for this problem.
As an aside, what the heck to computers mean by 'unexpected error' anyway? What kind of error is 'expected? I think it is just programmers having fun at our expense.
Good luck. Let us know how it turns out.