Google is reporting a service issue with Google Calendar, starting at 10:22 AM today. The latest Google Status information is available at:
https://www.google.com/appsstatus#hl=en&v=issue&sid=2&iid=cc21ebe3962430b2e4ae2b52e3dde98f
We will provide update when they become available.
Please accept our apologies for any inconvenience this issue may have caused.
UPDATE: Google provided an update at 1:13 PM indicating that the problem was resolved.
-Computing and Communications Services