Cannot modify header information

Warning: Cannot modify header information - headers already sent by (output started at /home/www/guru.upl.dk/wp-content/plugins/events-and-bookings/events-and-bookings.php:606) in /home/www/guru.upl.dk/wp-includes/pluggable.php on line 1179

Im getting this error when trying to setup the event calendar. Any ideas to what could be going wrong?