I am running PHP 5.4.3 on MAMP PRO 2.1. I have removed all the WP files and reinstalled it and the Eventbrite still gets the error. I have also deactivated the Calendar PRO to see if that was messing it up, but it still errored on activation.
I switched back to the Twenty Eleven theme and I got the same error. The only other plug-ins I have active are the Events Calendar and Events Calendar PRO. The plug-in will not activate because of the error message. The other two Event Calendars did just fine.