I am getting the following Fatal PHP Error on my site. Can

Hi
I am getting the following Fatal PHP Error on my site. Can you please tell me how to fix it?

Thanks
Vandana

[20-Jan-2015 02:12:36 UTC] PHP Fatal error: Uncaught exception 'Google_ServiceException' with message 'Invalid json in service response: ' in /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/gcal/io/Google_REST.php:74
Stack trace:
#0 /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/gcal/io/Google_REST.php(37): Google_REST::decodeHttpResponse(Object(Google_HttpRequest))
#1 /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/gcal/service/Google_ServiceResource.php(178): Google_REST::execute(Object(Google_HttpRequest))
#2 /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/gcal/contrib/Google_CalendarService.php(569): Google_ServiceResource->__call('list', Array)
#3 /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/class.gcal.php(1258): Google_EventsServiceResource->listEvents('53sehcs35j4gnqm...', Array)
#4 /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/class.gcal.php(1222): AppointmentsGcal->import_and_up in /home/newstressclinic/public_html/wp-content/plugins/appointments/includes/gcal/io/Google_REST.php on line 74