In the 'Sticky blocks' admin page, if the 'Recent Activity' block is added to a 'Community type page, the following PHP 'Fatal error' message is displayed:
"
Fatal error: Call to undefined function: print_recent_activity() in /var/www/intranet/moodle/blocks/recent_activity/block_recent_activity.php on line 27
"

This appears to be becasue a required library file has not been included.

Out solution is to add the following line to the start of moodle/blocks/recent_activity/block_recent_activity.php:
"
require_once("$CFG->dirroot/course/lib.php");
"