I'm currently running into an issue were a user receives the following fatal error if they do not have the permission to create the "Event" content type the calendar is generated from. The pages are displayed using the view templates provided and the "Add Event" link is enabled.
Unsupported operand types in public_html/sites/all/modules/calendar/calendar.module on line 172
The line in question is from the calendar_menu_local_tasks_alter() function:
// The add new content page would redirect to the new event
// if we did not override that here. This way they will
// redirect back to the calendar.
$item['localized_options'] += array('query' => array());
Let me know if there's anything else I can provide to help locate what could be causing this.