I keep getting this error message and have tried on two different machines with the same results.
Fatal error: Smarty plugin error: in /media/hda1/www/openemr/interface/main/calendar/modules/PostCalendar/pnincludes/Smarty/Smarty.class.php on line 2008
Unfortunately that message is not very helpful. You might check that the directory interface/main/calendar/modules/PostCalendar/pnincludes/Smarty/plugins exists, contains some .php files, and is readable by the web server.