The problem with Google Calendar should be resolved.
See: http://www.google.com/appsstatus#hl=en&v=issue&ts=1380697199000&sid=2&iid=db569d823f54053b8be2072c944722ba for additional details.
Affected in what way:
Affected users were receiving a "Server error" message when attempting to access the Calendar service. Affected Outlook Users were receiving a "cannot connect to server" message when attempting to sych calendar(s).