Same here.
Not going to worry about it for a while, I'll give it until tomorrow to sort itself out..
Probably something going on on the server end and not locally as I've made no changes.
I'll wait and investigate further if it persists.
I just closed Outlook and noted that it hung on the taskbar notification area (closing).
Used task manager to end that task.
Restarted Outlook and it seems OK for now