As of 3:00pm on June 30th, Google reported the problem is corrected.

Original post:

As of 9:45am, Google reports problems with Google Calendar. When attempting to view the Google apps calendar you get:

Server Error:

Google Calendar is temporarily unavailable. Please try back later. In the meanwhile, you might find useful information on our Help Group and Help Center. We apologize for any inconvenience.

For more information see:

http://www.google.com/appsstatus#hl=en&v=status